1, the author's way. Many retrieval systems have author index and institution index, and patent literature retrieval systems have patentee index. The methods of searching from the names of authors, editors, translators and patentees or the names of institutions and groups through these indexes are collectively called author methods.
2. Title method. Some retrieval systems provide retrieval methods by title, such as title catalogue and periodical catalogue.
3. Classification method. Searching documents according to the subject classification system. This method is based on the knowledge system, which is convenient for us to find documents from the subject range and can play the role of "analogy". Classified retrieval mainly uses classified catalogue and classified index.