Simple stats: there are roughly 600 "uses" of the Bible, which include:
citations (naming a passage by reference in the main text),
quotations of a verse or passage in text,
allusion to a word, phrase or theological theme within the text,
marginal reference with book, chapter, and verse(s)
There are only a few of 1. but they are interesting for their rarity.
Quotations 2. occur frequently, sometimes but not always supported by 4. marginal references.
The third category of allusion 3. is the ground for admitting that a total is only a rough one. There is certainly language in the description of the celestial city, for example, that I have not individuated as instances of allusion to Revelation once the most obvious allusions are accounted for. Allusions, because unacknowledged in the text could come about in Bunyan's writing in a number of different ways, which bears thinking about, in the same way that biblical words and phrases might crop up in Christian conversation because they inhabit the speaker's imaginative world and functioning vocabulary - without necessarily intending deep theological exegesis of the originating passage.
More on 4. later...