Ramanujam–Samuel theorem

In algebraic geometry, the Ramanujam–Samuel theorem gives conditions for a divisor of a local ring to be principal.

It was introduced independently by Samuel (1962) in answer to a question of Grothendieck and by C. P. Ramanujam in an appendix to a paper by Seshadri (1963), and was generalized by Grothendieck (1967, Theorem 21.14.1).