eLibrraryUSA http://elibraryusa.state.gov/resources.html has been around for sometime and it is a great tool in the hand of researchers. It contain a lot of information that is tailored to your specific research need. You can also attend their weekly in training in the American embassy at Lagos every Tuesday. There you learn about how to use online tool both open and private or closed site.
A registration with them will give you access to millions of literature from all over the world. it will aid your research work

http://elibraryusa.state.gov/resources.html

Use it and thank me later