: Infinite series and differential equations. Distinctive Features

The book is written in Italian and is available in paperback or e-book format. The PDF version, which you might be looking for, is likely to be a scanned or digitized version of the book.

Many Italian universities (La Sapienza, Federico II, UniBo) have agreements with Liguori. If you log into your university's "Biblioteca Digitale" with your student credentials, you can often download a legal of the book for free, directly from the publisher.