Derivation of the Schrödinger equation from scale invariance

It is shown that ff one postulates an equation of nonrelativistic quantum mechanics in the form $\partial\psi/\partial t=f(V,\psi,\psi^*)$, where $V$ is the potential energy, and requires that this equation, like the action (of the usual form) be invariant under the group of transformations $\mathbf x\to\lambda\mathbf x$, $t\to\mu(\lambda)t$, and also imposes certain other weak restrictions, these conditions uniquely lead to the Schrödinger equation.