BÁRDI, I. THE LEAST ACTION AND THE VARIATIONAL CALCULUS IN ELECTRODYNAMICS. Periodica Polytechnica Electrical Engineering, [S. l.], v. 23, n. 2, p. 149–162, 1979. Disponível em: https://pp.bme.hu/ee/article/view/4828. Acesso em: 19 may. 2024.