  Chapter 4 of my book [1] is dedicated to Lie-B\"acklund group analysis of
various types of differential equations. The Russian edition of this book had
an Addendum (pages 262-266) containing a summary of new results (obtained by
the end of 1982) on classification of evolution equations of the second and
third order possessing Lie-B\"acklund symmetries. The \textit{Addendum} was not
included in the English translation of the book by technical reasons. I present
here the missing translation. In order to make the text self-contained, I have
added in the translation the equations from the main body of the book used in
the Addendum.
