The word is copyright not copy write. Whether a credit has to be given depends upon the arrangements made between the photographer who made the photograph(s) and the person who ordered the photos. If permission to publish without credit was given, then it is OK.
The Real Business of Photography
The Photographer's Guide to Negotiating
Selling Your Photography
|Waffles with fruits by Coolinarka|
from Food photography (desserts)
|Vestrahorn Frozen Reflection by Will B Milner|
from Ice cold