Question: Who did more ring theory, Cahit Arf or Sind ibn Ali?
Sentence (from "Arf invariant of a knot"): If "F" is a Seifert surface of a knot, then the homology group H("F", Z/2Z) has a quadratic form whose value is the number of full twists mod 2 in a neighborhood of an imbedded circle representing an element of the homology group.
Relevant evidence: No