"Limited to those of a strictly reference character, and to the most useful works in the English language, with some exceptions in other languages."
Critical and bibliographical notes, "references," prices, etc. The section Bibliography (pages [65]-79) includes titles of works on Choice of books, Children's literature, and Library economy.
"Books and articles on reference books and reference work": pages [6]-8. "Suggestive list of 100 reference books": pages [80]-82.