Given the two-component spinor ψ ψ R define its conjugate as χ χ L = − − η η ω ω ψ ψ R ∗ ∗ . It is not hard to show that D R ψ ψ R = − − η η ω ω ( δ δ L χ χ L ) and that therefore, if D R ψ ψ R = 0 then also δ δ L χ χ L = 0 and therefore that