The document you are reading was originally conceived (in 1995) as a reprint collection; the text was intended to serve as an introduction to what I believed to be some of the important papers in the field. A number of personal and editorial circumstances have prevented me from finishing this work; the LaTeX files have been frozen in my hard disk since May 2000, and, expectedly, reflect the perception of the field I had at that time. Therefore, this document can only be seen as some kind of draft, besides being somewhat outdated. Moreover, you will also find passages which may sound odd without the reprinted papers: perhaps you can make up your own reprint collection by binding the papers together with these pages (when I have found a featured paper to be freely available on the web, a link to a locally-cached online version of the paper is given for convenience; authors of missing papers are kindly requested to contribute them if they are allowed to do so: mailto:mlf@dlsi.ua.es).
Some of the material has already been published as journal papers or book chapters (Carrasco et al., 2000; Forcada and Carrasco, 2001), but the rest was not available in any way. A couple of months ago it occurred to me that this document might be useful to other people working in related fields, and, since I am basically switching to a different field of computer science, I have decided to hang it up on the web for whatever you wish to do with it. In fact, if you are really interested in using some of this material for your own publications or course notes, just contact me and I will be glad to pass the LaTeX sources on: you are just kindly asked to mention me and this website in the derivative work you produce.