John Cotton Dana,
A Library Primer — Chapter XXIII, Author numbers or book marks
(1899)
“ In a very small library the books in a given class can be distinguished one from another by writing after the class-number of each book the number of that book in its class. If the class-mark of religion, for example, is 20, the books successively placed in that class will bear the numbers 20.1, 20.2, 20.3, etc.Fiction should have author-numbers only. The absence of a class-number will sufficiently distinguish it from other classes. ”
