How do you say plagiarize in Russian?
For the original material, but with reliable/correct results:
Partial Differential Equations: Sources and Solutions (Dover Books on Mathematics) by Arthur David Snider
You too can create a compendium of solved problems using Dr. Snider's software (a contribution to a scholarship fund is requested but not required), called USFKAD, available at the USF website (info in the text Preface). - The software results can be a little hard to follow which is possibly why Handbook of Linear Partial Differential Equations for Engineers and Scientists has the errors it has.