We show that if R is a Jordan Szabó algebraic covariant derivative curvature tensor on a vector space of signature (p, q), where q ≡ 1 mod 2 and p < q or q ≡ 2 mod 4 and p < q − 1, then R = 0. This algebraic result yields an elementary proof of the geometrical fact that any pointwise totally isotropic pseudo-Riemannian manifold with such a signature (p, q) is locally symmetric.Since A λ = Aλ, E λ = Eλ. Both A and A λ preserve each generalized eigenspace E λ . The operator A is said to be Jordan simple if A λ = 0 on E λ for all λ. We say λ is an eigenvalue of A if dim{E λ } > 0; the spectrum Spec {A} ⊂ C is the set of complex eigenvalues of A.Lemma 1.1. Let A be a self-adjoint linear map of a vector space of signature (p, q).(1) We may decompose V = ⊕ Im (λ)≥0 E λ .(2) We have E λ ⊥ E µ if λ = µ and λ =μ.(3) The spaces E λ inherit non-degenerate metrics of signature (p λ , q λ ). (4) If λ / ∈ R, then p λ = q λ .