Diaries and letters
MLA
Nicolson, Harold, and Nigel Nicolson. Diaries and Letters. [1st American ed.] New York: Atheneum, 1966-1968
APA, 7th edition
Nicolson, H., & Nicolson, N. (1966-1968). Diaries and letters. [1st American ed.] New York: Atheneum
Chicago, 17th edition
Nicolson, Harold, and Nigel Nicolson. Diaries and letters. [1st American ed.] New York: Atheneum, 1966-1968