APA

Gartside L., . (1981). Model business letters. London: The English Language book Society.

Chicago

Gartside L, . 1981. Model business letters. London: The English Language book Society.

Harvard

Gartside L., . (1981). Model business letters. London: The English Language book Society.

MLA

Gartside L, . Model business letters. London: The English Language book Society. 1981.