“…Also, in the linear case, the equations K01-1 (Kennedy et al, 2001), W95-1 and N93-1 (Nwogu, 1993) reduce to the same equations, and here we will refer to them as N93-1 when dealing with linear aspects. Similarly, S13-1 , G12-1 (Galan et al, 2012) and M98-1 coincide in the linear case, and we will refer to them as M98-1.…”