The Berenstains met in art school and built on Stan's early success placing cartoons in the Saturday Review of Literature to become a successful magazine cartoon team in the 1950s -- high-profile assignments that brought them to the attention of children's book publishers. They eventually published through Theodor Geisel's Beginner Books imprint at Random House with the above work, The Big Honey Hunt. The official site is here, with a fine, brief biography here; you can see some Berenstain work before the Bears here. The published obituaries thus far are reporting that there are more than 200 books featuring the Bears.