FYI: Here is a helpful resource when looking for sources for certain topics for your essays and research papers. It is a source shared by other universities sorted by certain subjects that will assist you when researching. Below you will find the video link explaining the DCN and how to access it. This resource is free to all.
http://community.ashworthcollege.edu/videos/4198
Hopefully this resource will help all those in need of a place to go for sources to cite for your hand-graded assignments. Have a great day and happy learning! 
Khaysee