He went on to develop a theory of double-valued formal groups that led to the calculation of cobordism rings of complex manifolds having symplectic coverings and to the explicit construction of what are now known as  Buchstaber manifolds.
He proceeded to formulate a theory of two-valued formal groups, which resulted in the computation of cobordism rings for complex manifolds with symplectic coverings and led to the creation of what are now referred to as Buchstaber manifolds.