M- Monographs (including works on history and chronicles in ancient books)
Essays
Newspaper articles
Journal articles
Doctoral dissertation
R- research report
S standard
patent
A—— Precipitated documents in monographs and papers.
Z—— Other unspecified literature types
Electronic document types are identified by two letters:
database
computer program
Electronic bulletin
For electronic documents with non-paper carriers, the carrier type shall be indicated in the reference mark:
A database on an online network
Database/tape database
M/CD-CD books
CP/DK disk software
J/OL- online log
EB/ol- online electronic bulletin
You can judge by these letters.