As already said, the study of ordered sets has long been almost exclusively devoted to that of lattices. Things started to change in the 1970s and, since then, hundreds of papers have been concerned with other ordered sets, in particular with finite ones. It would therefore require several copious books to describe just the principal results obtained in this field (in comparison, the “Handbook” on Boole algebras published by Elsevier in 3 volumes has 1440 pages). However, with regard to books, the situation has not changed much. Whereas there exist dozens of books on lattice theory, the number of books on ordered sets is still very low and the latter are often concerned with particular aspects. That is why we have given, in the last section of each chapter, a number of notions and important results, referring the reader to the (numerous) references allowing us to know more on these subjects. Below, we give some marks and indications to help the reader find his bearings among these references and, more generally, in the documentary resources of the field.

Internet and the inescapable Google

If we ask that search engine, for instance, for “partial order dimension,” we obtain almost 14 million answers, with many appropriate references in the first pages. It is then clear that Google may be a very efficient tool, even though important – but old – references may not be found.