1. O. Bjo̸rgum, Arbok Univ. Bergen, Mat. Nat. Ser. Nr. 1 (1951).
2. C. Trueadell,The Kinematics of Vorticity(Indiana University Publication Sci. Ser. No. 19, 1954).
3. Note on the existence of steady viscous Beltrami flows
4. We exclude the possibility that there are surface curves which are straight and parallel to V∑ and extend to infinity in both directions.