The library has several electronic databases which can be searched at great speed for articles in thousands of periodicals. Several of these databases, including Ebsco and Infotrac, have full text of articles, while others, such as CARL Uncover, only provide author, title and enough information to find the article in the library. You can consult Astronomy Periodicals in the University Library to eliminate articles which are too difficult. See also How to Get a Better Grade on Your Paper . Two good places to start are Favorite Astronomy Links and Educational Resources in Physics and Astronomy .
Search engines are fast ways to search the web.
You may want to take advantage of some of the many forms of Research Help and Library Instruction provided by the good people of the library. In my courses I am also asking you to include a bit more. This is the simplest case. You may cite books in any style which includes all of the above and which is consistent. The title of a book is printed in italics.