Grammatically Correct: The writer's essential guide to punctuation ...

GRAMMATICALLY CORRECT
By convention, small caps are employed for certain abbreviations:
A.M. and P.M.; A.D. and B.c. (or c.E. and B.C.E., for Common Era and
Before the Common Era). For design reasons, they are sometimes
used to make up the opening word or words of an article or chapter.
They also have a few specialized applications that may be peculiar
to a particular publication or genre: For example, they may be used
for the name of each speaker in a magazine interview, for synonyms
in a dictionary, or (in combination with initial full caps) for the title
and author's name on a book cover. In business and technical writing,
small caps are often used instead of full caps for abbreviations and
acronyms.
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