APA
Encyclopaedia Britanica, . (1990). The New Encyclopedia Britannica Macropedia , Vol.21. Chicago: University of Chicago.
Chicago
Encyclopaedia Britanica, . 1990. The New Encyclopedia Britannica Macropedia , Vol.21. Chicago: University of Chicago.
Harvard
Encyclopaedia Britanica, . (1990). The New Encyclopedia Britannica Macropedia , Vol.21. Chicago: University of Chicago.
MLA
Encyclopaedia Britanica, . The New Encyclopedia Britannica Macropedia , Vol.21. Chicago: University of Chicago. 1990.