Are there any additional requirements for naturalization?

Yes. The following are additional requirements:

• Residents must demonstrate good moral character for the five years (or three years, if married to a U.S. citizen) prior to applying for citizenship. Many criminal convictions are seen as evidence of a lack of good moral character.
• Men who lived in the U.S. as permanent residents when they were 18 to 26 years old should have registered for the draft.
• Employed permanent residents should have filed U.S. income tax returns each year.