MLA

Lao, Dazhong, and Shanshan Zhao. Fundamental Theories and Their Applications of the Calculus of Variations. Springer Singapore, 2021.

APA

Lao, D., & Zhao, S. (2021). Fundamental theories and their applications of the calculus of variations. Springer Singapore.

Chicago

Lao, Dazhong, and Shanshan Zhao. Fundamental Theories and Their Applications of the Calculus of Variations. : Springer Singapore, 2021.