1. A. Kriščiūnaitė, Almost contact structures on hypersufaces of a four-dimensional centro-biaffine space of elliptic and hyperbolic type,Liet. Mat. Rink.,7, 423–438 (1967).
2. N. M. Ostianu and T. F. Laptev, On pairs of distributions in manifolds of an almost complex structure, in:Abstracts of Commun. of Fifth All-Union Conference on contemporary problems of geometry, Samarkand (1972),
3. A. Baškienė, Structures that are induced on submanifolds of an almost complex manifold,Liet. Mat. Rink.,16, 23–34 (1976).
4. W. Boothby and H. Wang, On contact manifolds,Ann. Math.,68, 721–734 (1958).
5. J. Gray, Some global properties of contact structure,Ann. Math.,69, 421–450 (1959).