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We may use Stokes' Theorem to deduce this by applying it to a tiny rectangle 
  normal to the w1 direction with sides obeying one of dw2  = 
  0 and dw3  = 0, and then cyclically permuting the indices. 
  The surface integral in Stokes' theorem then becomes
u2u3dw2dw3(![]()
v)1
while the path integrals become

which gives us:
