W. Schroder et Hj. Treder, The general-relativistic and covariant form of the first Helmholtz vorticity theorem, FOUND PHYS, 30(11), 2000, pp. 1975-1982
The general relativistic and covariant differential form of Helmholtz's fir
st vorticity theorem is presented. We prove in relation with it an invarian
t kinematic identity which is the generalisation of the Helmholtz theorem f
or general continua.