Citation management software can save you time in organizing and using the citations to books and articles you have collected.   The Northwestern University Library supports three different softwares:

• Endnote is a proprietary software that is free for Northwestern students, faculty, and staff, during their tenure and Northwestern.   It is the most powerful of these systems, but has the highest learning curve.
• Zotero is an open-source, Web-based system.
• Mendeley is another open-source, Web-based system.