## Reference request for RR-index

Let R be a noetherian domain with field of fractions F, let V be a finite-dimensional F-vector space, and let M,N⊆V be R-lattices in V (finitely generated R-submodules of V containing a basis for V over F). We define the R-index of N in M, written [M:N]R, to be the R-submodule of F generated by … Read more