[B2] T.F. Banchoff, Triple points and surgery of immersed surfaces, Proc. Amer. Math. Soc. 46 (1974) 402-406.The author proves that the number of triple points in an immersion of a smooth or polyhedral surface is congruent modulo 2 to the Euler characteristic of the surface.
10/12/94 firstname.lastname@example.org --
The Geometry Center