NGS Style Manual‎ > ‎- A -‎ > ‎

ACRONYMS

Except when they have entered the language as words (radar, flak, Anzac), acronyms are in full caps, no spaces or periods.

Long acronyms may be reduced in type size for the sake of appearance.

Use a or an according to the pronunciation:
        an AIDS researcher, a UNESCO program.

Plurals add lowercase s: WASPs.

acronym