  The main stages of development of the theory of superconductivity in systems
with overlapping energy bands are formulated. The main references on the
classical papers of the author of this theory, Prof. Moskalenko V.A., and his
coworkers are listed. The list also includes papers related to high -
temperature superconductivity. Some peculiarities of the two - band model,
which lead to qualitatively new results in comparison to the usual one - band
model, are enumerated. We also list our own publications on thermodynamics and
collective oscillations in the two - band systems which are based on a
generalization of Moskalenko model of systems with overlapping energy bands for
the case of a reduced density of charge carriers.
  Application of the two-band model to the description of thermodynamic
properties of the compound $MgB_{2}$ is also discussed.
