Equation Icon  ∫ f (⃗y) ∮ [ 1 ∂g (⃗y) ∂ ( 1 )] d3y------- = − 4πg(⃗x) + dSk -----------k-− g(⃗y)--k- ------- . (101 ) N∕B |⃗x − ⃗y| ∂(N∕B) |⃗x − ⃗y| ∂y ∂y |⃗x − ⃗y|