TY - JOUR AU - B. S. Kruglikov TI - Some classification problems in four-dimensional geometry: distributions, almost complex structures, and generalized Monge–Ampere equations JO - Sbornik. Mathematics PY - 1998 SP - 1643 EP - 1656 VL - 189 IS - 11 UR - http://geodesic.mathdoc.fr/item/SM_1998_189_11_a2/ LA - en ID - SM_1998_189_11_a2 ER -