What do the English letters in the references stand for? What is M.N.C.D ... and what does it stand for?
According to GB3469-83 "Document Types and Document Carrier Codes", it is marked with a single letter: m-monograph (including historical records in ancient books) c-collection of essays n-newspaper article J-journal article D-dissertation R-research report S-standard P-patent A-separation of monograph and collection of essays.