APA
GRAY A., . (1950). Gray's manual of botany: A handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. New York: American Book Co.
Chicago
GRAY Asa, . 1950. Gray's manual of botany: A handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. New York: American Book Co.
Harvard
GRAY A., . (1950). Gray's manual of botany: A handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. New York: American Book Co.
MLA
GRAY Asa, . Gray's manual of botany: A handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. New York: American Book Co. 1950.
