Cita APA (7th ed.)

Sagan, H. (1969). Introduction to the calculus of variations. McGraw-Hill.

Cita Chicago (17th ed.)

Sagan, Hans. Introduction to the Calculus of Variations. New York: McGraw-Hill, 1969.

Cita MLA (9th ed.)

Sagan, Hans. Introduction to the Calculus of Variations. McGraw-Hill, 1969.