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As an example of using the notion of normalized classes to investigate symmetry properties of differential equations, we completely solve the group classification problem in the class of $(1+1)$-dimentional nonlinear Schr?dinger equations $i\psi_{t}+\psi_{xx}+ \mid\psi\mid^{\gamma}\psi+ V(t,x)\psi=0$, where $\gamma$ is a real non-zero constant and $V$ is an arbitrary complex-valued potential depending on $t$ and $x$.
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