Who did more ring theory, Cahit Arf or Sind ibn Ali?
Cahit Arf:  He is known for the Arf invariant of a quadratic form in characteristic 2 (applied in knot theory and surgery theory) in topology, the Hasse–Arf theorem in ramification theory, Arf semigroups, and Arf rings. Sind ibn Ali: He is known to have translated and modified the Zij al-Sindhind. Sind ibn Ali:  As a mathematician Sind ibn ʿAlī was a colleague of al-Khwarizmi and worked closely with Yaqūb ibn Tāriq together they calculated the diameter of the Earth and other astronomical bodies.
i don't know