Caveat lector - Let the reader beware
When you use a research or academic library, the books, journals and other resources have already been evaluated by scholars, publishers and librarians. Every resource you find has been evaluated in one way or another before you ever see it. When you are using the open resource site, none of this applies. There are no filters. Because anyone can write it, documents of the biggest range of quality, written by authors of the biggest range of authority, are available on an even playing field. Excellent resources reside along side the most dubious.
From Evaluating Internet Information
The databases contained in this guide allow you to easily access scholarly/peer-reviewed articles. If you do a Google search for information, 99% of the information you find will most likely NOT be peer-reviewed or scholarly.
