Solomon I. KHMELNIK. Study on Principle Extremum of Full Action. Newest Updates in Physical Science Research Vol. 12, [S. l.], p. 120–128, 2021. DOI: 10.9734/bpi/nupsr/v12/11452D. Disponível em: https://stm.bookpi.org/NUPSR-V12/article/view/2636. Acesso em: 4 jun. 2026.