Please answer the following question: I know that the answer to the question "What does Nanjing University library contain?" is in "Nanjing Library, founded in 1907, houses more than 10 million volumes of printed materials and is the third largest library in China, after the National Library in Beijing and Shanghai Library. Other libraries, such as city-owned Jinling Library and various district libraries, also provide considerable amount of information to citizens. Nanjing University Library is the second largest university libraries in China after Peking University Library, and the fifth largest nationwide, especially in the number of precious collections.". Can you tell me what it is?
A:
precious collections