Following the maturation of woodblock printing, official, commercial, and private publishing businesses emerged while the size and number of collections grew exponentially. The Song dynasty alone accounts for some 700 known private collections, more than triple the number of all the preceding centuries combined. Private libraries of 10–20,000 "juan" became commonplace while six individuals owned collections of over 30,000 "juan". The earliest extant private Song library catalogue lists 1,937 titles in 24,501 "juan". Zhou Mi's collection numbered 42,000 "juan", Chen Zhensun's collection lists 3,096 titles in 51,180 "juan", and Ye Mengde (1077–1148) as well as one other individual owned libraries of 6,000 titles in 100,000 "juan". The majority of which were secular in nature. Texts contained material such as medicinal instruction or came in the form of a "leishu" (類書), a type of encyclopedic reference book used to help examination candidates.