Let 𝒪 be an integral domain containing the rational numbers, Σ its quotient field, D a derivation of Σ, and 𝒪′ the ring of elements in Σ quasi-integral over 𝒪. It is shown that if D𝒪⊂𝒪, then D𝒪′⊂𝒪′.
© Copyright 1966 Pacific Journal of Mathematics. All rights reserved.