Equation Icon  − det𝒒 = 1 + |βƒ—∇y |2 + |βƒ—∇z |2 + (βƒ—∇y × βƒ—∇z )2, (254 ) γ = Γ , γ = Γ + ∂ Xr Γ . (255 ) 0 0 a a a r