  The virial theorem for the translation-invariant theory of a polaron [3] is
discussed. It is shown that, in [3], Tulub made a nonoptimal choice of
variational parameters in the strong-coupling limit, which led to the violation
of the virial relations. The introduction of an additional variational
parameter to the test function reduces the polaron energy and makes it possible
to satisfy the relations of the virial theorem for a strong-coupling polaron
(the Pekar 1 : 2 : 3 : 4 theorem).
