[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 dpvc@geom.umn.edu --
The Geometry Center