Equation Icon  a b ℒξ(E ⊗s E )ηab = 0 , (160 ) ℒ ξR4 = ℒ ξR7 = 0 , M -theory (161 ) ℒ ξH3 = ℒ ξϕ = ℒ ξRk = 0 . Type IIA/B (162 )