Literature research assignments will often require you to use "secondary sources," which provide literary criticism, interpretation, and historical context for your topic.
Examples of secondary sources are journal articles and books.
After finding a "starter" source or two from the resources linked here, try the "Books" and "Databases" links to find journal articles, books, and other types of sources.
The background databases and reference series' listed here are great for finding your first source! Then dig a little deeper by looking for books and journal articles using the "Books" and "Databases" links.