Equation Icon  [ α ] 1- α′ [ α ] 1- α′ gβ′;γδ = − 2R β′γ′δ′, gβ′;γδ′ = 2R β′γ′δ′, (5.15 ) [gα ′ ′] = − 1R α′′′ ′, [gα′ ′ ′] = 1-R α′′ ′′. β;γδ 2 βγ δ β ;γ δ 2 β γδ