"We can request them from whatever or whoever is in charge of the train." Wen Qing points at the huge tomes that are her textbooks, then holds them out for Aziraphale to inspect. The anatomy book is clearly not from earth, since it covers both humans and a large number of non-human species, while the book about molecular biology looks fairly normal.

"I can't tell if the train produces the things we ask for or procures them from... somewhere. Point is, you can either request a specific book you know, or you can request books on specific topics such as I did when I requested these books. There is even a catalogue of books from a large number of worlds."