What are the common methods for manually detecting second-hand information?

Common methods for manual detection of second-hand information include common law, retrospective method and subsection method. According to the common methods of information retrieval by querying related public information, segmentation is one of the common methods of second-hand information retrieval. The common methods of manual retrieval of second-hand materials are common law, backtracking and segmentation. Manual retrieval is a traditional retrieval method, that is, using reference books (including books, periodicals, catalog cards, etc. ) retrieve information manually. The common methods of manual retrieval of second-hand information are truncation, common law, tracking and segmentation. Manual retrieval does not need special equipment, and users can use relevant retrieval tools according to the retrieved objects. The method of manual retrieval is simple, flexible and easy to master.