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Current-definition freedom in a derivative-coupling model.

The problem of the construction of a covariant current operator in a two-dimensional field theory is reviewed and subsequently applied to a recently proposed derivative-interaction model. It is found both by solving the equations of motion as well as by path-integral techniques that there exists a family of admissible solutions labeled by a parameter xi, only one choice of which corresponds to that previously derived. This is shown to be in agreement with results for the other known soluble two-dimensional field theories in which a gauge principle is absent.