The symbol codes of the standard format of references are as follows:

Types of references: monographs [M], essays [C], newspaper articles [N], journal articles [J], dissertations [D], reports [R], standards [S], patents [P], and precipitated documents in the collection of papers [A].

Types of electronic documents: database [DB], computer [CP], electronic bulletin [EB]

The carrier types of electronic documents: Internet [OL], CD [CD], magnetic tape [MT] and disk [DK].