2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/62501In this paper we find the explicit formulas of two dimensional commuting ($2\times 2$)-matrix differential operators which were introduced by Nakayashiki. The common eigen functions and eigen values of these operators are parametrized by the points of principally polarized Abelian varieties.LaTeX, 20 pagesAlgebraic Geometrytext