According to GB3469-83 "File Types and File Carrier Codes", reference file types and file types are identified by a single letter:

Monograph-m; Newspaper-n; Journal-j; Patent literature-p; Compile-g; Ancient books-o; Technical standard-s; Dissertation-d; Science and technology report: reference tool-K; Search tool-w; Document-b; Audio tape-a; Chart-q; Record-l; Product sample-x; Video tape-v; Meeting minutes-c; Chinese translation-t; Music score-I; film-y； Manuscript-h; Microfilm-u; slide-z； Microfilm-f; Other-e.

Requirements for the number of references:

(1) The number of references must be not less than 5, and it is better to have more than 10.

(2) Read more books on financial analysis and financial management and master relevant theories, but don't mark too many books on teaching materials in the cited references. Generally no more than two books.

(3) Try not to cite master's or doctoral dissertations, even if the number of citations does not exceed 1.

(4) Cite at least 1 English literature.

Reference to the above content: Baidu Encyclopedia-References