Fundamental theories and their applications of the calculus of variations
  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.