“…where t α , t q and t T are the notations for the thermal displacement gradient, the heat flux, respectively the temperature gradient, in the three-phase-lag heat conduction theory, K ij and K * ij representing the tensor of the thermal conductivity, respectively the tensor of the conductivity rate. The results of applying the three-phase-lag theory to particular materials, a theory that comes from the dual-phase-lag theory, see [2,29,43], have been studied in many papers, for example in [3,5,6,12,13,24,25,28,30,36,38], other studies presenting the advantages of this theory, such as [1,9,39].…”