If you go to the creative commons licensing page for the image, it will tell you what and to whom you must give attribution. In some cases, just the author, sometimes the derivative author, or both, and sometimes they require stating the type of licensing used, with a link to that. I don't usually mess around with images that require a whole book's worth of attributions. There are so many images you can find that are either Public Domain or simply require attribution to one person/author.

I have a training on this, that might be of help: Google Images that you CAN Use - Part Two, Follow-Up Training

You're very welcome Hilda, I was surprised there was not a lot of information on attributing Flickr CC images because they have heaps to use so I had to share it here :)

Sharing this will help many more members here.