Veterinarians generally derive some of their income from selling several manufacturers' lines of pet-care products  Knowing that pet owners rarely throw away mail from their pet' s veterinarian unread, one manufacturer of pet-care products offered free promotional materials on its products to veterinarians for mailing to their clients
Very few veterinarians accepted the offer, however, even though the manufacturer's products are of high quality
The special promotional materials were intended as a supplement to the manufacturer's usual promotional activities rather than as a replacement for them.