Reports
Reports are usually informational publications produced by government organizations or professional groups. They may contain some recommendations for future actions, and will usually contain statistics and descriptive material about the issue of concern. These reports are often available as digital publication (but may be print-only if they date from before digital publishing was available).
Books are a good source for connecting your topic to the "larger picture" by bringing in history or the social context (why your topic is important, etc.). You don't have to read the entire book to have it as a source-- you can use a smaller part of it if you like.
Videos and DVDs include both streaming online video and physical DVDs at the library. These are great sources for images, interviews, and (sometimes) statistics.
This sample search of "green tea" in the image below found over 79,508 books, articles, videos.
(click on image to enlarge)
