TY - JOUR AU - A. A. Andronov AU - E. A. Leontovich TI - Sufficient conditions for the “structural instability of the first degree” of a dynamical system on the plane JO - Differencialʹnye uravneniâ PY - 1970 SP - 2121 EP - 2134 VL - 6 IS - 12 UR - http://geodesic.mathdoc.fr/item/DE_1970_6_12_a1/ LA - ru ID - DE_1970_6_12_a1 ER -