There's a copy of Mary Roslin Williams's book on ebay. I got a copy some time ago and I know they aren't always too easy to find:

http://www.ebay.com/itm/Advanced-Labrador-Breeding-by-Mary-Roslin-Williams-1988-Hardcover-/321482103792?pt=US_Nonfiction_Book&hash=item4ad9d39bf0