The books in the library are usually arranged according to the call number. Call number, also known as shelving number, is a set of numbers indicating the shelving position of documents in the collection, which is used for extraction and shelving. It usually consists of letters, numbers and other symbols. The call number consists of classification number, species number and auxiliary identification number.

The auxiliary distinguishing numbers are mainly version numbers and volume (volume) numbers. Among them, the version number is used to distinguish different versions of the same book, which is generally written after the book number (species number). The version number is represented by Arabic numerals, and the number is preceded by =, and 1 version is not written. Starting from the second edition, different translations and revisions of the same book should be regarded as the same edition; Volume numbers are used to distinguish different volumes of multi-volume books. The volume number is located after the version number and is preceded by:. If there is a volume under the same volume number, it can be represented by (), usually after the version number and represented by Arabic numerals.