People say that a book you can't find doesn't exist

I recall that for a while, even though the situation was so desperate, Brauer spent all his time bringing his card index up to date. He was finding it increasingly hard to find the books he was looking for. People say that a book you can't find doesn't exist. ... Classifying twenty thousand volumes is no easy matter. Not only do you have to have a strict respect for order - an almost superhuman respect, I would say - but you need a method and time to devote to the thankless task of cataloging works whose meaning is very different from the numbers you use to identify them.

C.M. Dominguez, tr. P. Sis, The house of paper (2004), 48-9