Second attempt is:
I'm really sorry, but if you produced these pictures I can't credit whoever you are because you are not named in the magazine. This makes me really cross, I use other peoples work here to understand what they have done and to learn from them, they should take credit for what they have created. If anyone looks at work that has been produced it should be possible for them to find out who the artist was so that they can commission work of their own if they so choose. It is unthinkable that an author of a written piece is not credited or the musicians on a record and film credits list everyone. What is the problem with illustrators?