  The powers of generating functions and its properties are analyzed. A new
class of functions is introduced, based on the application of compositions of
an integer $n$, called composita. The methods for obtaining reciprocal and
reverse generating functions, and solutions of the functional equations
$F(A(x))=G(x)$, where $A(x)$ is an unknown generating function, are proposed.
  Key words: generating functions, reverse, reciprocal, composita, method.
