Fractional differential equations: change of variables and nonlocal symmetries

In the work point changes of variables in different types of fractional integrals and derivatives are considered. In a general case fractional integrodifferentiation of a function with respect to another function arises after such change. The problem of extending a group of point transformations to operators of this type is considered, corresponding prolongation formulae for the group infinitesimal operator are constructed. Usage of prolongation formulae for finding some nonlocal symmetries of the equation and checking their admittance is demonstrated as a simple example of an ordinary fractional differential equation.