APA Style
Writing Business Letters. (1978).
Indonesia:
Elex Media Komputindo.
Chicago Style
Writing Business Letters.
1st edition.
Indonesia:
Elex Media Komputindo,
1978.
Text.
MLA Style
Writing Business Letters.
1st edition.
Indonesia:
Elex Media Komputindo,
1978.
Text.
Turabian Style
Writing Business Letters.
Indonesia:
Elex Media Komputindo,
1978.
Print.