“…An expression for the exact solution of ()–() was presented in Rodríguez et al [
13], as a preliminary problem resulting from applying the method of separation of variables to an unidimensional wave equation with delay. In that context, the condition
was assumed, writing
, but, as shown in Jornet [
14], where it was applied to solve a more general multidimensional wave equation, it is straightforward to adapt the expression given in Rodríguez et al [
13] to the case
. Notwithstanding, these expressions do not seem to be suitable for constructing an exact numerical scheme, and so providing the basis for an efficient computational method.…”