TY - JOUR AU - D. A. Popov TI - Asymptotic behaviour of the positive spectrum of a family of periodic Sturm–Liouville problems JO - Izvestiya. Mathematics PY - 2009 SP - 579 EP - 610 VL - 73 IS - 3 UR - http://geodesic.mathdoc.fr/item/IM2_2009_73_3_a5/ LA - en ID - IM2_2009_73_3_a5 ER -