The paper classification number marks the classification of the paper, and the paper classification number is compiled according to the following principles:

1, accuracy: the classification number should accurately reflect the research field and theme of the paper, and cannot be randomly selected or mislabeled.

2. Specificity: the classification number should be specific, that is, avoid using too broad or vague classification numbers as much as possible, so as not to affect the retrieval and utilization of papers.

3. completeness: the classification number should be filled in completely, including the classification number, document type identifier and species number, so that librarians can classify and put the papers on the shelves.