Blue ring binder of papers, labelled 1992/41 to 1993/09. The first is “On the Energy Levels of the Hydrogen Atom”.

22 of the 25 binders in the collection contain final versions of preprints as they appeared in the preprint series of the University of Cambridge, Caltech, and other associated institutions. The ones contained were those authored by Hawking or his students and close collaborators.

Preprints are a typical stage in the path of an academic paper towards its publication. They tend to be versions that are ready for peer review, intended for circulation among peers before or during the peer review process. Much actually fruitful scientific communication is done via preprints rather than finalized articles: by the time a scientific paper is officially published, experts in the field have likely already read and commented on earlier versions, and learned from them what is relevant for their own work. Before the 1990s, preprints were generally issued by academic departments, in small print runs of dozens to hundreds; or more informally as photocopies. Many academic departments and research institutions have an officially run preprint series, with (somewhat) standardized numbering and formatting. With the advent first of e-mail and newsgroups, and later online preprint depositories such as ArXiv, the vast majority of circulation has moved online. Since the mid-1990s, printed versions of preprints have become almost symbollic.