Zhang Liyan 
How to Express Rhetorical Questions in Mandarin [PDF ebook] 

With the requirements of Putonghua learners to understand and memorize a number of character pronunciations, and with view to major characters that Cantonese may be confused with, this book selects 60 groups of examples that are illustrated and analyzed in a popular way. With the use of learning tips and cartoon illustrations, it will help learners be alert to the mistakes they frequently make in the character pronunciation of Putonghua.