Parser, is the book you're referring to called The Elements of Style?
See the link below for an interesting article on that book and the so-called that/which rule, which, apparently, is not a rule at all. In other words, either "which" or "that" can be used to introduce a restrictive clause.
50 Years of Stupid Gram
mar Advice - The Chronicle Review - The Chronicle of Higher Education
***NOT A TEACHER***
Jasmin, good morning.
Thank you for your kind note.
(1) The book that I used is WOE IS I by Patricia T. O'Conner.
(2) She worked at THE NEW YORK TIMES.
(3) As I mentioned, she wrote her book for ordinary folks like me.
(4) I thank you for the link. I shall certainly TRY to read it. THE CHRONICLE is certainly too intellectual for an ordinary person such as I.
(5) I have always believed that "that" should be used for restrictive clauses.
(6) I have also heard that very many people acquainted with the history of English say that "rule" is nonsense.
(7) I shall continue, however, to use the "rule."
(8) Furthermore, since learners crave rules to give them self-confidence, I believe that learners should follow that "rule."
Thank you again for your reply -- and the link.
Have a nice day!