While the best answer to this question will always be at your local library, the reality of modern computing has completely changed the answer to this question since it was originally written.   Today, the easiest way to find academic references on volcanoes (or anything for that matter) is online.   Many libraries have subscriptions allowing direct access to journal articles for students – otherwise, articles are generally available for purchase.  

 A good first stop is Google Scholar.

Studying Volcanoes / Volcanology