“…At most one of the partial derivatives ∂ŵ ∂ai (z;ǎ,b), ∂ŵ ∂bj (z;ǎ,b), (z;ǎ,b) ∈ V, i = 1,· · ·, A, j = 1,· · ·, B − 1, vanishes, and thus, in case K > 2: ∂ŵ ∂ai (z;ǎ,b) = 0, ∂ŵ ∂bj (z;ǎ,b) = 0, for at least one i ∈ {1,· · ·, A} or j ∈ {1,· · ·, B − 1.} (21) The latter conclusion cannot be drawn in case K = 2; however, see the forthcoming Remark 5.8. Note that always K 2.…”