Il. Buchbinder et al., GENERALIZED CANONICAL QUANTIZATION OF A BOSONIC STRING MODEL IN MASSIVE BACKGROUND FIELDS, Nuclear physics. B, 1997, pp. 280-283
A method of constructing a canonical gauge invariant quantum formulati
on for a non-gauge classical theory depending on a set of parameters i
s proposed and then applied to the theory of a closed bosonic string i
nteracting with massive background fields. It is shown that within the
proposed formulation the correct linear equations of motion for backg
round fields arise.