When obtaining permission to include content in your newsletter or magazine, get that permission in writingto create proof or a trail of your permissions. Develop a file system to document permissions with, if possible, a search mechanism to help you locate permissions as you receive them. This way you can easily and quickly search these permissions when using the same content in another manner or in an additional publication. Also, if another publication, website or content aggregator asks to reproduce your newsletter, you can check your permissions system to determine what content you may relicense to others.
See on www.copyrightlaws.com