2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/155286We extend relative oscillation theory to the case of Sturm--Liouville operators $H u = r^{-1}(-(pu')'+q u)$ with different $p$'s. We show that the weighted number of zeros of Wronskians of certain solutions equals the value of Krein's spectral shift function inside essential spectral gaps.16 pagesSpectral TheoryMathematical Physics34B24, 34C10 (Primary); 34L15, 34L05 (Secondary)text