Some classificational problems in four-dimensional geometry:   distributions, almost complex structures and Monge-Ampere equations
  In this paper we consider three deeply connected classificational problems on four-dimensional manifolds. First we consider and describe locally regular distributions. Second we give a classification of almost complex structures of general position in terms of distributions. Finally we classify nondegenerate Monge-Ampere equations with two variables in terms of e-structures. 
Boris S. Kruglikov (Moscow State Technical University n.a. Baumann)