CHUMAK, O.; SUSHKOVA, N. Operator of Photon Density in the Phase Space. Ukrainian Journal of Physics, [S. l.], v. 57, n. 1, p. 30, 2012. DOI: 10.15407/ujpe57.1.30. Disponível em: https://ujp.bitp.kiev.ua/index.php/ujp/article/view/2021360. Acesso em: 6 feb. 2023.