On hypercomplex pseudo-Hermitian manifolds
  The class of the hypercomplex pseudo-Hermitian manifolds is considered. The flatness of the considered manifolds with the 3 parallel complex structures is proved. Conformal transformations of the metrics are introduced. The conformal invariance and the conformal equivalence of the basic types manifolds are studied. A known example is characterized in relation to the obtained results. 
Kostadin Gribachev, Mancho Manev, Stancho Dimiev