Currency: The timeliness of the information.
Relevance: The importance of the information for your needs.
Authority: The source of the information.
Accuracy: The reliability, truthfulness and correctness of the content.
Purpose: The reason the information exists.
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http://www.lib.ncsu.edu/tutorials/evaluating-sources/
What is a scholarly source?
Scholarly sources (also referred to as academic, peer-reviewed, or refereed sources) are written by experts in a particular field of study and serve to keep others, especially those in the field, current on the most recent research findings, and news. These resources will provide the most substantial and highest quality information for your research papers.
What is peer-review?
When a source has been peer-reviewed it has undergone the review and scrutiny of a review board of colleagues in the author's field. They evaluate this source as part of the body of research for a particular discipline and make recommendations regarding its publication in a journal, revisions prior to publication, or, in some cases, reject its publication.
Why use scholarly sources?
The authority and credibility evident in scholarly sources will improve the quality of your paper or research project. Use of scholarly sources is an expected in academic course work.
Now, you will have direct links into library resources from Google Scholar.
Be sure to enter Google Scholar through the Libraries Database list.
That way, you will not have to keep signing in. 
Primary Sources are original records created at the time historical events occurred or well after events in the form of written or oral memoirs.
Examples include:
Secondary sources are documents written after an event has occurred, providing secondhand accounts of that event, person, or topic..
Examples include: