Thank you very much Paul.

If you can, please let me know the details of the book you use.

If you are a serious student of English grammar, I can recommend:

A Student's Introduction to English Grammar.

By Rodney Huddleston & Geoffrey K. Pullum

Published by Cambridge University Press

ISBN: 978-0-521-61288-3

Here's a link:

http://www.cambridge.org/gb/academic/subjects/languages-linguistics/grammar-and-syntax/students-introduction-english-grammar

You can buy it on the Cambridge website for about GBP22.

PaulM