J. K. S. Kamassury, D. P. Meira Filho, C. da R. Silva, J. B. S. . Pampolha Júnior, R. D. R. da Silva, and A. R. . Pinto, “Calculation of the creation and annihilation operators of a free particle in the light cone coordinate formalism”, J. Eng. Exact Sci., vol. 7, no. 4, pp. 13317–01, Oct. 2021.