  The Cartan equivalence method is utilized to deduce an invariant
characterization of the scalar third-order ordinary differential equation
$u'''=f(x,u,u',u'')$ which admits the maximal ten-dimensional contact symmetry
Lie algebra. The method provides auxiliary functions which can be used to
efficiently determine the contact transformation that does the reduction to the
simplest linear equation $\bar{u}'''=0$. Furthermore, ample examples are given
to illustrate our method.
