A surface which is homeomorphic to a finite collection of spheres, each with a finite number of handles, cross-handles, cross-caps, and perforations. A preliminary version of the classification theorem of surfaces states that every surface is ordinary.
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ReferencesFrancis, G. K. and Weeks, J. R. "Conway's ZIP Proof." Amer. Math. Monthly 106, 393-399, 1999.
Referenced on Wolfram|AlphaOrdinary Surface
Cite this as:
Weisstein, Eric W. "Ordinary Surface." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/OrdinarySurface.html