Equation Icon  [ ] Aα′β′ = [Ω α′β′,] A α′β′γ′ = Ω α′β′;γ′ − A α′β′;γ′, [ ] A α′β′γ′δ′ = Ω α′β′;γ′δ′ − A α′β′;γ′δ′ − A α′β′γ′;δ′ − Aα′β′δ′;γ′. (6.2 )