On semiprime comultiplication modules over pullback rings
Following some ideas and a technique introduced in [Algebra Discrete Math. 2009, no. 1, 1–13] and [Colloq. Math. 120 (2010), 23–42] we give a complete classification, up to isomorphism, of all indecomposable semiprime comultiplication modules with finite-dimensional top over a pullback of two valuation domains with the same residue field.