There were several ways to unravel one's target bibliography to begin research. A library's card catalogue was an excellent means to find sources on the subject (these were cards arranged in little drawers, organized alphabetically, with references by author, book title, and subject). Finding a recent book on the target subject would provide a bibliography of recent credible sources, and that would begin the trail to find other sources and expend the net of available sources on a subject.

Of course, articles provided the most up-to-date research and bibliographies. Professional journals usually published hard copy indexes of recent articles, which included subject references. Articles could be used in the same way as a recent book's bibliography to unravel the appropriate sources for research on a subject.

Attendance at conferences was also a viable way to learn about available sources. I also wrote letters to scholars seeking advice of research topics (letters were pieces of paper placed in envelopes and sent by the Postal Service - you needed to apply a purchased stamp). And publishing articles resulted (as it still does) in quick feedback as to what sources one might be missing.

The library card catalogue system (and the Library of Congress published card catalogue) were excellent sources and led to a path of discovery different from the internet. The latter is superior in many ways, but anyone who used a card catalogue misses them for the opportunity of serendipitous discovery.

Now if you want to know about the preparation of vellum and of inks from vegetable matter, you'll need to find someone else, because that is a year or two before my time. I go back to a previous century, but not that far back.