I've found myself accomplishing "referential accessibility" for ebooks by simply picking out a few words from the start of a sentence and asking someone to sear

I've found myself accomplishing "referential accessibility" for ebooks by simply picking out a few words from the start of a sentence and asking someone to search for it. Unlike page numbers, they are consistent across multiple printings, and can point to a specific location much more easily (second sentence in the third paragraph on page 231 is terrible). Overall, it seems to work reasonably well.