Equation Icon  ( ¯) --------- u α, β ab − u-(β,α¯)ab = − i∇ [aXb ], ( ) (3.11 ) u (α, ¯β) + u (β,α¯) = 1∇ X 𝜀cd + i 𝜀 ′ ′α ∇ ′β ¯C ′ − 𝜀 ¯β ′∇ ′ αC , (3.12 ) ab ab 2 c d ab AB (A B )C AB (A B)C