In addition to the helpful licensing that authors can put on their websites, Creativecommons.org allows you to search Google, Flikr, Yahoo, and more to find copyrighted works- for your own use (depending on stipulations). So given that, I went out and retrieved this image, using http://search.creativecommons.org/.
This work can be adapted, modified, or built upon. (so I did)
Original posted at: http://flickr.com/photos/circulating/225782567/