2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/76484We prove some new results which justify the use of interval truncation as a means of regularising a singular fourth order Sturm-Liouville problem near a singular endpoint. Of particular interest are the results in the so called lim-3 case, which has no analogue in second order singular problems.Spectral TheoryFunctional Analysistext