APA
Encyclopaedia Britanica, . (1990). 1991 Britanica Book of the year. Chicago: University of Chicago.
Chicago
Encyclopaedia Britanica, . 1990. 1991 Britanica Book of the year. Chicago: University of Chicago.
Harvard
Encyclopaedia Britanica, . (1990). 1991 Britanica Book of the year. Chicago: University of Chicago.
MLA
Encyclopaedia Britanica, . 1991 Britanica Book of the year. Chicago: University of Chicago. 1990.