Books Classification 130 History 54 Classification, Universal decimal 41 Reviews 33 Printing 23 Bibliography 21 Conservation and restoration 15 Prices 15 Subject headings 15 Periodicals 14 Library science 12 Book industries and trade 9 History and criticism 9 Cataloging 8 Bookbinding 6 Manuscripts 6 Books and reading 5 Booksellers and bookselling 5 Building 5 Collections 5 Exhibitions 5 Indexing 5 Libraries 5 Publishers and publishing 5 Statistics 5 Abstracting and indexing 4 Writing 4 Book design 3 Civilization 3