Evolution equations of the second and third order with Lie-B\"{a}cklund symmetries

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.