I’m going through the fragments of Eusebius printed by Angelo Mai in the 1820’s from catenas. These often refer pretty briefly to the sources from which he copied them. Thus one fragment is headed (translated):
From Macarius Chrysocephalus’ Florilegium, in Villoison, Anecdota, vol. 2, p.74.
Hum, yes, well of course.
Fortunately I can find information online, that tells me the book was printed in two volumes in 1781, that the author was “De Villoison”. Knowing that ligatures are not well handled by Google Books search engine, I search for author=Villoison and title=Anecdota, and behold! I find that the book is actually on Google books, here, the two volumes bound as one (the second volume starts on p.514 of the PDF).
Likewise I can find a mysterious volume by “R. Simon” which turns out to be A critical history of the text of the New Testament, here.
When I started on the Eusebius project, I travelled by car to Cambridge, spending around $60 in petrol to do so. I went to the University Library. I went to the admissions desk, and paid $15, and renewed my library ticket which had lapsed. Then I went to the Rare Books room (which only Privileged People are permitted to enter, with a letter of reference from an academic), and I ordered up the two editions of Mai’s book. Then I looked to see which pages I needed. Then I filled in a paper form, in pencil of course. Then I handed it in, with the books, and went away, and came back a week later. And then I paid 25c per page for a grainy photocopy. This I took home, turned into a PDF, and have used ever since.
How much easier and cheaper it was today, to find this source which I probably want only a few lines from! We are truly, truly blest!