  The problem of linearization for third order evolution equations is
considered. Criteria for testing equations for linearity are presented. A class
of linearizable equations depending on arbitrary functions is obtained by
requiring presence of an infinite-dimensional symmetry group. Linearizing
transformations for this class are found using symmetry structure and local
conservation laws. A number of special cases as examples are discussed. Their
transformation to equations within the same class by differential substitutions
and connection with KdV and mKdV equations are also reviewed in this framework.
