W. Dicks et J. Llibre, ORIENTATION-PRESERVING SELF-HOMEOMORPHISMS OF THE SURFACE OF GENUS-2 HAVE POINTS OF PERIOD-AT-MOST-2, Proceedings of the American Mathematical Society, 124(5), 1996, pp. 1583-1591
We show that for any orientation-preserving self-homeomorphism alpha o
f the double torus Sigma(2) there exists a point p of Sigma(2) such th
at alpha(alpha(p)) = p: This answers a question raised by Jakob Nielse
n in 1942.