M and J in references are types of references, representing monographs and periodical papers respectively. C stands for prose
1. Common document types are identified by a single letter, as follows:
(1) journal [J] (journal)
(2) Monograph [M]
(3) Paper collection [c]
(4) Paper [D]
(5) patent [P] (patent)
(6) Technical standards (standardization)
Newspapers (articles)
(8) Science and Technology Report [R] (Report)
2. The type of electronic document carrier is identified by two letters, as follows:
(1) magnetic tape [MT] (magnetic tape)
(2) Disk [DK] (Disk)
(3) CD
(4) Online network [OL] (online)
The reference type identification method of electronic document carrier type is [document type identification/carrier type identification]. For example:
(1) online online database [DB/OL] (database online)
(2) Tape Database (Tape Database)
(3) CD monograph
(4) Disk software [CP/DK] (computer program on disk)
(5) Online log [J/OL] (serial online)
(6) Online bulletin board system [EB/OL]
3. Literature precipitated in monographs and papers [a];
Other unspecified literature types [Z]
Baidu Encyclopedia: Document Type Recognition