Published in 2016 by Industrial Press USA, the technical parts of this version in English have been entirely rewritten to illustrate an implementation of the Demand Driven Adaptive Enterprise DDAE model starting with a DDMRP pilote. It also introduces the Demand Driven Skill Model DDSM using the Skill buffers.
The novel is the official resource used as a business case in the training Adaptive Enterprise Foundations AEF of the Demand Driven Institute DDI.
The technical sheets are available on this web site as well as the more advanced descriptions of the DDSM published in the appendixes of the following two books by Carol PTAK and Chad SMITH:
The Demand Driven Adaptive Enterprise (Industrial Press 2018) and Adaptive Sales and Operations Planning (Demand Driven Press 2022 ).
Publiée en 2005 par les éditions Afnor et réédité en 2008 et 2012, cette édition en français accompagnait le programme Basics of Supply Chain Management BSCM de la certification CPIM de l’ASCM (ex APICS).
Les parties techniques du roman policier retracent la mise en place du modèle de planification de la supply chain MRPII.
Les fiches techniques sont en annexes du livre.
August 7, 2023
J'ai eu l'occasion de lire ce livre (la version anglaise) il y a quelques années. On ne trouve guère une telle œuvre, alliant suspens (pour la plage), solutions pratiques (pour l'après-soleil) et un nouveau cadre de management de la supply chain (pour la rentrée). À ne pas manquer !
August 26, 2022
A business novel on supply chain, DDMRP and a small manufacturer!
I enjoyed this book for three reasons. First, it discusses the perils of small manufacturers. While the novel is set in France, the problems faced by H. Rami are common to most US small manufacturers, a cash shortage, missing due dates, long lead times, constant changes to orders, frequent equipment breakdowns, and not enough hours in the day to address all the fire fighting. Second, Caroline Mondon gives a 10,000-foot view of several tools, usually available to large manufacturers, that might have significant potential for small manufacturers if only they could reduce the fire fighting. She introduces Demand-driven MRP, Sales and Operations Planning, ISO14000, total productive maintenance, flow concepts, and employee evaluations. Third, she does items 1 and 2 wrapped around the unfolding clues in an interesting mystery. Nice job!
November 19, 2021
I really loved reading the Missing Links! It's the very first time I came across a captivating novel with soo many learning insights. I started and finished it right away! I recommended it to the whole Air Liquide S&OP Community. Well done!
May 1, 2021
Hi Caroline, I read your book Missing links and I loved it. I work in Strategic Sourcing director in the produce industry. I want to continue my development in Supply Chain and DD Erp is a topic that called my attention since we need to improve product freshness and OTIF. I was wondering if you can recommend me how to continue my development (training, books, online content)?
January 14, 2021
Votre ouvrage m’a bien aidé dans mon travail. C'est la bonne idée : écrire une histoire à suspense incluant les principes de bonne gestion d'entreprise. Ludique, sérieux, ce livre apporte de judicieuses actions pour bien gérer sa boîte !
January 01, 2021
The Missing Links is an excellent read to get started on the thought process for Demand Driven. It´s a must for supply chain professionals.
Je viens de terminer la lecture de votre livre The Missing Links. Quel livre incroyable! Je voudrais vous dire un grand merci pour avoir écrit une story aussi merveilleuse. Tout d'abord, j'aime tout ce qui est français, qui a probablement commencé à mon plus jeune âge lorsque j'ai entendu le port de bras et la ronde de jambe à mes cours de ballet. De nos jours, j'aime tout ce qui est français - le vin, la campagne, la culture, la nourriture et les Français. Votre roman allie d'une belle manière l'art de vivre à la française avec le supply chain management, mon autre "hobby". J'aimerais entrer en contact avec vous sur LinkedIn et j'espère qu'un jour on pourra se rencontrer aussi en personne.
December 25, 2020
I recently read The Missing Links. It was a fantastic introduction to DDAE. I look forward to following your insights.
May 17, 2020
Caroline Mondon a parfaitement su rendre les différents sujets très compréhensibles grâce à la mise en situation des héros qui se retrouvent confrontés à une entreprise dans laquelle la situation générale est proche de la catastrophe et qui ne connaissent rien à sa gestion. Les personnages apprennent les différentes ficelles du supply chain management, et nous apprenons de façon très pédagogique avec eux.
J'avais lu l'ouvrage "le chaînon manquant" (quasiment le même ouvrage, mais en français) lors de ma formation CSCP de l'APICS et cela m'avait vraiment aidé à appréhender les différents sujets de la formation grâce à des mises en situation qui permettent de bien visualiser les problématiques rencontrées et les notions supply chain à utiliser pour les résoudre.
J'ai relu il y a quelques mois "the missing links" pour me rafraîchir globalement la mémoire sur les différentes notions dans le cadre de mon travail. C'est léger et ça remet les pendules à l'heure. Les documents disponibles en ligne via des liens en annexe sont très bien écrits et permettent d'approfondir et bien comprendre les notions de certains sujets. Pour finir, il est très enrichissant de lire l'introduction au DDMRP, une méthode qui permet de maîtriser la chaîne d'approvisionnement 'end-to-end' et qui repose sur un flux tiré par la demande.
Un grand bravo et un grand merci à Caroline MONDON !
November 25, 2019
The Missing Links is a great read, and incorporates Supply Chain and Operations principles effectively. The subject is woven into the novel in a simple manner without being simplistic. I am already recommending this to everyone, wanting to get into Supply Chain as a career and those looking to expand their knowledge beyond the stereotyped processes we've been working with for years.
September 17, 2019
This is a good read in every way if you want to learn more about how the supply chain works!
September 14, 2019
A good book for your summer ! A real easy way to learn how DDMRP will help in a small company too.
August 25, 2019
Just finished reading the book! Fast pace and entertaining while you learn the SC basic concepts and methodologies. Really enjoyed it.
September 10, 2019
Brief story of successful business practices
Fast reading novel combined with the learnings of managing a complete organisation. Although not entering in details on how to implement the different methodologies, it gives you a good grasp of the basic processes you need to put in place to make your business a successful one.
Since I read the Goal, almost 20 years ago, I have always searching for the next level in Supply Chain thinking. Caroline takes us on this journey and starts right from the beginning, making all the connections and showing the added value of all the great Supply Chain thinkers. She ends her juicy story with some final clues, solving the mystery and providing clear message that S&OP is ready to keep on evolving! Great work!
March 4, 2019
July 22, 2019
A good introduction to the requirements for business in the 21st century. introduces Lean/6 Sigma and demand driven concepts. Based very much on the Goldratt model.
July 25, 2018
Recently I have bought a copy of « the missing links ». Last weekend, I have read half of the book and balance in the coming weekend. It is such an amazing book, much better than « the goal ». Technical concept presented in such a novel way and very interesting to read. Congratulations for the same.
May 2, 2018
Definitely a must-read book! I really appreciated this novel which will find its rightful place on my bookshelf, right next to The Goal. 7 good reasons to read it:
The Missing Links is a well written novel, easy to read and riveting to the end
The action takes place a in a small / mid-size company, the type of which we would like to see more in our countries
It introduces in a nice way all the concepts which are - or should be - our daily bread in supply chain, making the links among DDMRP, Lean, TOC, TQM, … you name it.
All these theoretical concepts come to life with practical tools and methodologies
More important, the novel put people at the center of the game. Ethic is not a vain word for Caroline Mondon, who reminds softly the social and environmental responsibility of companies
The novel features a management consultant who is the model we strive for: competent without being arrogant, benevolent, practical, eager to transform and to drive concrete results
Last but maybe not least, the main character plays the cello! A soft point for me ;)
March 12, 2018
When I first read the French version of the Missing Links a couple of years ago, I was impressed by how much I learned from it (supply chain mangement, management of change...), without effort! I'm only halfway through this new edition and I can already see that it is state-of-the-art and includes demand driven methodologies. Bravo Caroline MONDON and thanks Richard Cushing for your review.
March 7, 2018
Nice book indeed full of insights. Easy and pleasant to read. I can only recommend it. Well done Caroline MONDON and thank you Richard Cushing for this relevant review
March 3, 2018
Great read! Highly recommend this one next to the pool on a Saturday morning! Best spot to get some reading done is a beach in Spain. Thanks Caroline MONDON for the good read.Missing links is an excellent book not only for someone looking to embark on their Demand Driven journey but anyone getting involved in a supply chain management role.
It just took me less than 2 days and part of a night to read the breathtaken "Missing Links", written by Caroline Mondon. It is one of these books that once you begin you don't let it go until you have finished. The story is great with a lot of suspense and intriges and on top of it you get introduced to the quite heavy topic of "Demand Driven Supply Chain" in a very pleasant and motivational way. And the content goes far beyond Supply Chain Management: Any current and future Manager/Leader should read this book and then ask him/herself how to connect the Missing Links in his/her own company. The book also provides great connexion and understanding between "Supply Chain Management", "Lean" and "Theory of Constraints".
August 29, 2017
July 12, 2017
Très bon livre. Plein de bon sens et de pragmatisme.
Au delà des concepts demand driven bien introduits, le livre décrit le chemin à parcourir managerialement, techniquement, et éthiquement parlant.
June 11, 2017
It's a great book if you are starting out into the amazing world of supply chain and want to have a basic understanding of various supply chain and associated methodologies such as Lean, Six Sigma, Theory of Constraints etc. The concepts are explained well and help a reader understand the challenges and complexities of supply chain management.
As "The Missing Links" will lay the DDMRP foundations for you, the next logical book to deep-dive into is "DDMRP" by Carol Ptak and Chad Smith.
March 3, 2017
Combining the logic and musical passion of SME supply chains in regional France
This is a must read for anyone in the entrepreneurial / Turnaround space.
The Missing links is a Detective novel which leads while its teaches the logic and passion of doing business in regional France. It is a business novel in the Socratic style of “the Goal” by Eli Goldratt. But with the added flavour of a Micheal Lewis (Liars Poker, Big Short, the UnProject. Plus others). In building the story line and desires of the unlikely heroine Heloise.
The setting of the story in Tours, give a uniquely French country side fell to the complexities in today’s complex supply chain and component.
I think Caroline Mondon’s book will appeal to a number of audiences. One group are those who seek to understand the complexities, problems & pressures faced in today’s supply chains and SME, this a great place to start. The problems that Heloise face are all too real. Caroline has provided valuable reference in the form of clues. The corresponding website is useful reference of tools and methods to over come these common business problems. The content of the Demand Driven method, demonstrates the current and in my view the only method that sustainability deals the Supply / Demand Chain complexity.
This book would be a suitable for the business turnaround , family offices and those facing business generational change. The sleepless nights, and gut feels that Heloise had to make on the fly is very typical of the change that all SME business leaders experience.
In summary this book can appeal to logical and emotional side of business.
It took me 4 days to read. I would recommend once, then come back again and look at the toolkit and interdependencies that will help with the Supply / Demand Chain complexity.
There is a whole lot of content in this delightful book.
March 1, 2017
A Wonderful Book!
The Missing Links is an excellent business novel, full of mystery and intrigue, but more importantly full of helpful information on continuous improvement. I highly recommend this book to everyone who not only own companies, but that also run companies. This is a story about a business which is just barely staying in business and how it manages to become a highly successful one. I especially like how one idea built on another and then another in the true “continuous improvement” spirit.
February 1, 2017
Reading this for the second time and finding even more depth , it is like peeling an onion, as more and more is revealed. Merci beaucoup.
December 24, 2016
Well written and riveting!
The Missing Links is a powerful story of business improvement, demand driven methodology and international intrigue. Well written and riveting, I could not put it down. Highly recommended to anyone looking to improve a business. For all levels of employees, not just top management.
December 6, 2016
Great book, really enjoyed it. Not only full of excellent demand driven supply chain management and Lean advice and information but also an intriguing “who dunnit” and glimpse into French life – from hunting to music and food
A super introduction to learn more about the secrets of demand driven supply chain management, all in the disguise of a catching detective novel. The detective novel leads you into this exciting world of supply chain management in a very skillful, entertaining and interactive way. Be prepared to learn in a fun and efficient way! Very well done!
October 25, 2016
I am picked my kindle and reading at the plane between flights. Having excessive training schedule between 4 cities and the book is becoming my friend.
October 24, 2016
October 13, 2016
As others have said the idea of covering business principles in a Novel makes this book very readable. The central message that comes across very srongly though is not that you use any particular techniques in your business but more about people and business relationships. Caroline uses lots of music analogies to get the point acorss that you have to have everyone playing in harmony get the best from the orchestra, and that if you build great supply chain relationships there are large business benefits to be had. Whether you use DDMRP to link it all together is proabably not the point….this book is thought provoking, it should make you think how to I get the my orchestra to play in time…..really enjoyed it..
How to change the thoughtware in your company!
This book describes the levers to change drastically your company, and gives you the tools and the road-map : Being in a bad situation, the management team of a company (in fact, it is very much like every other company…) discovers how to LINK people and departments inside and outside, then transform the supply-chain to boost the people and become profitable.
The style is rather like “The Goal” of E. Goldratt, so that it can be read by everybody, to popularize the supply-chain concepts (Kaizen tools, value-stream-mapping, S&OP, flexibility and multi-skill matrix, business strategy…). The appendix is a rich tool-box to manage the change. I particularly appreciated the competences / competitiveness plan, so powerful and unavoidable.
Get this book read by your teams, you will save time and energy!
October 9, 2016
I finished the book!
Congratulations. You have done a very clever job of combining an explanation of a real world need for S&OP with a mystery.
September 7, 2016
August 23, 2016
I like the concept. It is beyond a book: book + ebook.
There is an affiliated web site which transforms your book to something in between kindle & iphone.
There are notes on the margins to reach the web site and find more details about that point.
Web site is encouraging you to contribute and tends to evolve to be a portal. This is like updating your iphone. You have the paperback but also updated through the web site. A squarecode option could be inserted.
This book is good for SME scaled starters. I believe appendixes in the web site would be enrichened by variety and detail through time.
The book covers TLS (TOC – Lean – SixSigma) approach more than DDMRP hence converging to Epiphanized: A Novel on Unifying Theory of Constraints, Lean, and Six Sigma, Second Edition and Velocity: Combining Lean, Six Sigma and the Theory of Constraints to Achieve Breakthrough Performance – A Business Novel.
Compared to well known Goldratt books I could simply say that this is a business NOVEL rather than BUSİNESS novel. It structured like The Goal: A Process of Ongoing Improvement, there are wise guys explaining issues or thinking by themselves. Another relevant book in terms of supply chain replenishment is Isn’t It Obvious? Revised Edition and it explains the TOC way of replenishment, not DDMRP way.
To my understanding there are two main streams in TOC World: First one is staying with the original concept, represented by Israel, namely TOC. Second one is evolving to cover MRP for conglomerates, represented by USA, namely DDMRP and relying on TLS approach. This book is on the USA side. Since most of the continuous improvement efforts are in lean approach and combined with a goal statement to stay focused reader must be patient to see DDMRP traces for a while. Appendixes are exciting for DDMRP.
I do like several small touches in the book:
NLP : could be utilized to ease thinking process and layers of resistance
Esperanto : could make dealing with global supply chains easier
Common rehearsal : excellent demonstration to why and how we need to synchronize
Proverbs : there are elegant French philosophers’ quotations scattered around the book
Civic : humanist, feminist, environmentalist comments were attractive.
August 21, 2016
‘The Missing Links’ is an excellent detective novel, with a message of Manufacturing Operational Excellence that, I am sure, will do for Demand Driven Materials Requirements Planning (DDMRP) what ‘The Goal’ did for the Theory of Constraints (TOC). The ‘clues’ leading one to the on-line Appendix of additional information is a brilliant way of giving the reader extra information on many different aspect of Operations and Supply Chain Management. This book is definitely a must for anybody that believes operational excellence and supply chain management is their chosen career.
August 5, 2016
Charming story – an ideal introduction for students and those new to Supply Chain Management
Firstly, high praise to the author who has undertaken the time and effort to have this translated into this English version from it’s native French, and the maps included helped as my knowledge of the geography of France is not good.
The book was not exactly what I was expecting it to be, whilst it does make the occasional reference to Demand Driven, I would not say that is the core of it by any means. I was expecting it to be to DDMRP what “The Goal” was to Theory of Constraints, or what “The Goldmine” was to Lean. The term Demand Driven first gets mentioned about half way through the book, and it almost 200 pages in before Green/Yellow/Red buffers are mentioned. But some good demand driven info around distribution is mentioned in the final 20% and the Demand Driven way forward as the book concludes is very interesting. As there is a real buzz of interest around DDMRP at the moment, I can see why this book might want to grab onto the shirt tails.
Also, despite being called a Detective Novel, there is only a small thread of that intertwined through – it’s not like the Geoff Relph & Robert Irwin book “Who Murdered MRP?” ….. that one really is a solving a crime approach almost like a Cluedo whodunit, questioning the ‘suspects’ etc. The final ten pages or so of this book do reveal the mystery of Thierry Ambi’s disappearance and the blood stains in the ‘coop’.
But what I did particularly like is how we followed the main character Héloïse on her learning journey of understanding, – the gist of the story is that her father dies and she, a musician, not an industrialist, has to pick up the pieces and make it work. Because she admits lacking any SCM knowledge, the book builds up from ground zero – we have it explained what benchmarking is, what a balance sheet is, what the acronym ERP stands for etc. So I don’t think the book is aimed at execs and existing managers in the field, they would be better off reading the business novels by Bruce Nelson & Bob Sproull (‘Epiphanized: A Novel on Unifying Theory of Constraints, Lean, and Six Sigma, Second Editionand its sequel –Focus and Leverage: The Critical Methodology for Theory of Constraints, Lean, and Six Sigma (TLS)).) However, this one would be an excellent roadmap for any staff who moved into supply chain from other disciplines – especially as there is an accompanying website explaining various terms (numbered ‘links’ in the margins). The websites’ corresponding number is clicked on for any topic you wished to look up (TPM, 5S or whatever) and a detailed explanation is provided. Although the website was still a work-in-progress when I read ‘The Missing Links’ (excuse the pun) because a few definitions were yet to be populated and some were in French.
I’m sure it will prove a good hook for those who later embark upon APICS training, the LearnIt App gets a mention, and I suspect the serious game mentioned is a nod to The Fresh Connection simulation. Just enough for a reader to seek further information on various certifications that are eluded to (CPIM and CDDP).
One final point, hope not too picky, a word of caution before you hand the book to any strict vegetarians in your team, there is a passage contained within describing a Stag hunt with a pack of hounds, some people might find that a little less palatable than an anecdote of hiking boy scouts – but then again, the book is set in the French countryside, so I can see why it was included.
I loved the French edition and I was very happy to write the appendix on Supply Chain Talent Management for the English edition. A must read for SC professionals.
I am currently reading your book “The Missing Links”, and enjoying it too. I had seen it mentioned on the DDMRP LinkedIn group announcements. I am also following the clues on the associated website, I have a few comments here : …. Anyway. Great work.
July 15, 2016
“Excellence happens when your tools and processes are aligned with a shared vision, when there’s an understanding of the ‘why’ behind the actions….”
Following in the genre of The Goal, the now famous business novel by Eliyahu Goldratt, author Caroline Mondon presents us with The Missing Link – A Demand Driven Supply Chain Detective Novel. Mondon is a past-president ofFapics, the French Association of Supply Chain Management, and is also author of an award-winning and bestselling French business detective novel entitled Le chaînon manquant. This is her first novel in English.
Reading this book was a real treat!
While the mystery surrounds a character named Thierry Ambi, a brilliant and forthright consultant by the name of Lila Fractalle-Cass takes center stage in helping the H. Rami company emerge from the sudden passing of its CEO, a leadership vacuum, and its downward financial spiral.
The H. Rami company is suffering from all of the typical symptoms found in the vast majority of small to midsized business enterprises—and not a few giant conglomerates.
While struggling with the all-too-common “pyromaniac-firefighter” management methods, effective scheduling of production and replenishment becomes all but impossible.
So, just what is the pyromaniac-firefighting management method?
That’s simple: it means having an executive and management team that sets fires(unintentionally, of course) by applying bad policies and ill-informed metrics on the one hand, while taking extreme measures to put the fires out on the other hand.
This book is full of sound how-to advice and gems of wisdom woven into a fascinating story to keep the reader enthralled to the very end.
Here are a few gems and snippets to whet your appetite for this book:
“Scheduling in a company that tolerates ‘firefighting’ is probably one of the most difficult and stressful jobs on earth.”
“Little islands of excellence in a sea of mediocrity will not move a company forward.”
“It is only when you know the source of errors that you can then make improvements.”
“Excellence is the result of having mastered the what, the how, and also the why. Without the why’s you cannot motivate people to learn new things and pass this knowledge on to others.”
On Starting the Journey toward Ongoing Improvement
Author Caroline Mondon, in the midst of her novel, brings forward a compelling argument against those executives and managers of companies or supply chains who are trying to improve without articulating clear goals or developing a clear plan for improvement.
When you know where you are, and you can see where you want to go, you’re sure to get there in the end if you take a small step in that direction every day. And the good news is, the more steps you take, the more you’ll enjoy the journey, even if each step unbalances you a little bit. In fact, it’s precisely these small destabilizations that allow you to adjust your course to adapt to unpredictable external events. This way, you’re always getting closer and closer to your goal, even if your goal shifts somewhat. Remember, continuous improvement is a journey, not a destination.
Like men and women wandering aimlessly in a wilderness, we come across companies where there is no clear trajectory on a path of improvement. Instead, we find them retracing their footsteps over and over again—trying again and again the same tactics that have produced no durable improvements in the past.
If you and your management team are finding yourself wandering over the same ground again and again without lasting improvement, then I would suggest you read this book. This book is for CEOs, CFOs, supply chain managers, and anyone else involved in management of manufacturing, distribution or supply chains.
Read it! You’ll be glad you did.
« The missing links is a story of discovery, not unlike Alex Rogo’s journey in Eli Glodratt’s The Goeal. Today, many companies, not just in charming rural France, are plagued by similar problems : poor results, a disillusioned workforce, over-whelming complexity, variability, lost focus, and unclear priorities across all levels of operations and management. Héloïse, Caroline Mondon’s heroine, a passionate musician, sets out to save her family’s business and has the courage to face the inconsistencies and gaps between the way the business should work and reality. The solution to these is not just an operational one, and it is not easily found. In addition to effectively managing complexity and variability in her supply chain with a state-of-the-art Demand Driven Operating Model, she looks beyond planning and control to leadership and personal development.
Making complexity manageable through focused infusion of simplicity, driving out variability through buffering, replacing backward-looking- accounting with relevant information for decision making, eliminating conflicts through win-win solutions, and helping people make a positive contribution through unambiguous and inviting leadership : there are the links that turn an ailing enterprise around to reach a state of harmony and high operational and financial performance. When we leave our heroes at the last page, let’s take these insights to our own workplaces and add the missing links to make our own supply chains strong, for the benefits of our customer, our people, our societies, and our shareholders.
« ..like the clever plot of this detective novel which has clues weaving their way through the story, this book uncovers the mystery of how to implement best practices, and improve business processes and operations – all the while keeping you guessing as to « Who did dit ? »
Topical, relevant, and practical advice encompassed in a step-by-step methodology wrapped in a captivating storyline, which starts by turning the first page. »
“I wish all textbooks were written like this one! The Missing Links is easy to read and understand, written as a realistic story about the development of a factory, and set up as a detective story. The work is great for remembering supply chain management concepts. as an NLP Master trainer and International Leadership trainer, I especially enjoyed Caroline’s use of metaphors to enhance understanding and to use as memory hooks. This shows how you can ‘walk your talk,’ whether you are a president of a company or a student.”
“For more than 15 years, I have been involved with education in the field of sup-ply chain management. The Missing Links has been a real inspiration for showing how to explain both fundamental and advanced concepts of business management, supply chain management, and innovation. The storyline of the book makes it easy to understand the importance and leverage of supply chain management concepts, even for smaller companies. It was a pleasure reading about the development and transformation of a small traditional company into a modern, next-century enterprise. The way innovative concepts and methods have been applied in the book is logical and helps readers quickly get over a steep learning curve. I will definitely recommend this book to my supply chain management students.”
July 16, 2016
“The Missing Links by Caroline Mondon is similar to The Goal by Dr. Eli Goldratt, probably the best selling business novel ever written. Caroline has written a compelling story about a fictional, privately held manufacturing company that is facing serious challenges when the owner of the company suddenly dies, and his daughter is left to take over the business. It clearly explains the process necessary for a company to adopt the latest thinking about planning and management as the organization struggles to adapt to the changing needs of customers as they become ever more demanding. This book can be read by anyone with an interest in how businesses can be run more efficiently and effectively. ”
I REALLY enjoyed reading this book. Why should it be limited in its readership to only Supply Chain and Logistics Chain professionals? It is an interesting story and the subplot that involved the Ambi family makes it even more able to be a general reading novel.
April 21, 2016
Thank you for all your comments