TY - JOUR AU - Yu. P. Chuburin TI - On approximation of the ``Membrane'' Schr\"odinger operator by the ``Crystal'' operator JO - Matematičeskie zametki PY - 1997 SP - 773 EP - 781 VL - 62 IS - 5 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/MZM_1997_62_5_a13/ LA - ru ID - MZM_1997_62_5_a13 ER -