For people trying to find information about the bullmastiff breed, including its history and use since its development in the mid 1800's there are several excellent sources, but most sadly may be out of print.

Bullmastiff, The Peerless Protector, by Jack Shastid & Geraldine Roach....most recent book with excellent history, breed care, etc.

American Bullmastiff Association Bulletins....published 3 times a year to ABA members.

The Bullmastiff Illustrated Breed Standard, by Carol Beans

The Mastiff and Bullmastiff Handbook, by Olif

The Hoflin Annual Bullmastiff Editions

ABA ROM Registry of Merit, available intermittently from the American Bullmastiff Association

The Bulleye, Carol Beans Editor...no longer being produced, but back issues carry a wealth of breed specific historical and training information.