“…More precisely, the gradients ∂T /∂x i , i = 1, 2, are discontinuous at every point (0, 0, x 3 ), x 3 = 0. For the interested reader, the level sets {(x 1 , x 2 , x 3 ) ∈ R 3 | T (x 1 , x 2 , x 3 ) = r}, with r > 0, are displayed in Prieur and Trélat [16]. 2) Numerical approximation: Recall that inf Q r ↑ as r increases, i.e., the more moments we consider, the closer to the exact value we get.…”