2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/57571A basis of quasi-invariant module over invariants is explicitly constructed for the two-dimensional Coxeter systems with arbitrary multiplicities. It is proved that this basis consists of $m$-harmonic polynomials, thus the earlier results of Veselov and the author for the case of constant multiplicity are generalized.22 pages; a minor correction done; accepted by Mathematical NotesMathematical PhysicsCommutative Algebra81R12; 20F55text