What does Z mean in the reference?

Code z indicates other unspecified literature types.

Reference type:

According to GB3469-83 "File Type and File Carrier Code", it is identified by a single letter:

M-Monographs (including historical records 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

Extended data:

Description format of references

1? , journal author. Title [J] Title, year of publication, volume (issue): page numbers.

2. Monograph author. Title [m]. Version (first edition not recorded). Place of publication: publisher, year of publication: page number.

3. Author, title [c] and editing procedure, name procedure, place of publication: publisher, year of publication: start and end pages.

4? Author of the paper. Title [D] Save the location. Save unit. Year.

5? Title of patent document [P]. Country. Types of patent documents. Patent number. publication date