On the Elementary Solution for the Partial Differential Operator $\circledcirc_c^{k}$ Related to the Wave Equation. European Journal of Pure and Applied Mathematics, Maryland, USA, v. 11, n. 2, p. 390–399, 2018. DOI: 10.29020/nybg.ejpam.v11i2.3223. Disponível em: https://www.ejpam.com/index.php/ejpam/article/view/3223. Acesso em: 22 dec. 2024.