APA Style

Inc, E, B. (1975). The New Encyclopaedia Britannica : Macropaedia Volume 6 (15th edition). Chicago: Encyclopaedia Britannica, Inc.

MLA Style

Inc, Encyclopaedia, Britannica,. "The New Encyclopaedia Britannica : Macropaedia Volume 6". 15th edition Chicago: Encyclopaedia Britannica, Inc, 1975. Text.