The original material consisted of 25 numbered boxes starting around 1967, books and papers and electronic materials in other locations, plus documents stored in an office at the ILLC, University of Amsterdam, Science Park. The total size was around 25 meters. This has been reduced to some 6.5 meters, according to the procedure described below. The main focus throughout in the selection was on research and teaching, with some broader organizational activities as a supplement to complete the picture of activities.
A very strict selection has been made of available documents concerning the personal educational trajectory (school and university exams, materials around the dissertation and defense ceremony), as well as appointment papers, certificates for awards and honors, and material documenting more personal milestones, such as jubilees.
For publications, an informative selection has been made of: final manuscript (in the form of a reprint where available), one or at most two earlier manuscripts, correspondence with publishers, relevant correspondence with colleagues or students prior to or after publication. Not included are referee reports (which were very incomplete in the original archive), or subsequent official reviews. For monographs and textbooks (but not for edited books), the actual published volume has been added to the archive. Also not included, except when highly relevant, are prepublication reports on research.

The archive contained large numbers of private notes with ideas and possible projects: only a representative selection has been kept. Thirteen notebooks (1967-1983) with mixed personal and academic content have been placed in a private family archive. In addition, a number of larger incomplete projects for papers, books, and other scientific projects has been collected in chronological order under the heading Unfinished.

The correspondence has been trimmed considerably to retain only letters and printed emails (where available) with scientific topics. Personal or organizational messages between colleagues have been removed, and likewise, small matters such as requests for reprints or general announcements for academic activities. Also removed were academic recommendation letters written over the years for students and colleagues, and all correspondence of an organizational-administrative nature. (Many of these materials should be available in the archives of the relevant academic institutions.)

For courses taught, a selection has been made of announcements, correspondence, and test or exam materials. Moreover, all available lecture notes are present in the archive. For specific students supervised for masters theses and doctoral dissertations, a selection has been made of characteristic correspondence. These theses and dissertations themselves can be found in university archives.
For conference lectures, seminar presentations, or public talks, announcements have been kept, plus handouts, and materials such as correspondence relevant to the event.
For editorial work on special volumes or Handbooks, only a small selection has been made, including contracts, publicity items, relevant correspondence with publishers, and some characteristic correspondence with authors. Editorial work for journals is only listed, as detailed correspondence with contributing authors was not available.
For workshops and other events organized, a selection has been made of relevant materials, mainly original proposal texts if available, and the final programs.

Material concerning academic organizational activities was scarce in the archive to begin with, presumably because these documents are usually also available in the public domain for the relevant institutions (institutes, departments, universities, scientific funding agencies). What was available has largely been kept here, including original documents and some correspondence concerning the founding of the ILLC, the European foundation FoLLI, major projects such as the Dutch national cognitive science program, or international scientific initiatives. The archive contained no materials at all about standard academic activities such as memberships of committees of various sorts, tenures as dean of philosophy, mathematics and computer science, or the day to day running of various scientific projects. Even so, the materials present here do give a representative outline of the broader organizational and financing context for the individual research and teaching that is the main focus of this archive.
Finally, starting around 2000, and increasingly through the years, many items are only available in electronic form without prints, such as correspondence, earlier versions of published articles, or organizational materials. Electronic files with supplementary material for the period until the summer of 2017 have been added to this archive.