TY - JOUR TI - Essential spectrum of systems of singular differential equations T3 - Acta scientiarum mathematicarum AU - Ibrogimov Orif O. PY - 2013 LA - English SN - 0001-6969 UR - http://acta.bibl.u-szeged.hu/32903/1/math_079_numb_003_004_423-465.pdf ER -