Birational-integral extensions and differential modules (Q1065870)

A birational-integral extension A of a commutative Noetherian domain R (i.e. \(R\subset A\subset \bar R\), where \(\bar R\) is the integral closure of R) is said to be of ''cuspidal type'' if A coincides with the seminormalization of R in A. - The note contains a straightforward proof of the fact that any cuspidal type extension is obtained by a finite chain of constant subrings of some derivations.