“…Keeping in mind the study of the S-metric and the fact that ρ 01,03 = 0, ρ 03,13 = 0, ρ 02,03 = 0, ρ 03,13 = 0 while framing the leading terms not vanishing when a = 0, we get: R 01,03 ≡ ρ 01,01 ξ 1 3 + ρ 03,03 ξ 3 1 + (ρ 01,23 + ρ 03,21 )ξ 2 0 + ρ 01,02 ξ 2 3 + ρ 01,13 ξ 1 0 = 0 Then, taking into account the fact that ρ 01,12 = 0, ρ 02,12 = 0, ρ 12,13 = 0, we obtain similarly: R 01,12 ≡ (ρ 01,32 + ρ 03,12 )ξ 3 1 + ρ 12,21 ξ 2 0 + ρ 01,10 ξ 0 2 + +ρ 01,13 ξ 3 2 + ρ 01,02 ξ 0 1 = 0 The leading determinant does not vanish when a = 0 because, in this case, all terms are vanishing and we are left with the two linearly independent framed terms, a result amounting to ξ 1 3 = 0 ⇔ ξ 3 1 = 0 and ξ 0 2 = 0 ⇔ ξ 2 0 = 0 in the case of the S-metric in ( [19]). In the case of the K-metric, we may use the relations already framed in order to keep only the four parametric jets (ξ 1 3 , ξ 2 0 , ξ 1 0 , ξ 2 3 ) on the right side. We may also rewrite them as follows:…”