I like this link: Does Your Dog REALLY Want to be Petted? | eileenanddogs
And the how to greet a dog poster: Free Downloads: Posters, Handouts, and More! | Animal Behavior and Medicine Blog | Dr. Sophia Yin, DVM, MS
I think each dog will have preferences. I have 2 Chow mixes who will do a head bob to avoid being petted on the head and a third who will tolerate it but move her head sideways so that I am not petting the head. Other dogs head butt and like head petting.
Is there a science based reason in the book you are reading? I am always interested in that.