SkyServer’s About Astronomy and the SDSS website contain background material to help students and teachers understand the concepts in this project. In addition to SkyServer pages, the references below give more information about the topics covered in this project, and give information and perspectives that may be of interest.
Books
Kaler, James, Stars and Their Spectra, 1997
Web Sites
How Atoms Produce Spectra, a web page from Nick Strobel’s Astronomy Notes, an entire Astronomy 101 textbook available for free online.