To my knowledge, all graphics, backgrounds and images used in this site are in the public domain or in shareware files. If I have used an image without knowing, please advise and I will remove it. I have tried to list and provide links to sites that I used in developing this website. Any material used in this unit is free for teachers and students to duplicate and use in their classrooms. Please do not add any of this material to your own site without providing a link back to me because some of the files are copyrighted.