I can see them on the automap and hear the sounds they make but there I cannot reach them in the game. They will not appear in most levels. Especially on custom level sets.
Recent community posts
https://github.com/librarianofbabel/libraryofbabel.info-algo This is the original algorithm released by the site author but admittedly it is for an image version of the library. But I did manage to dig up his email so you could possibly ask him to release the text version of it: email@example.com