I would like to sponsor a dear Russian friend's visit to the U.S. in September. To that end, I downloaded the form in:
In the above form, I'm asked in Section 1 to indicate the Naturalization Certificate number but It's been so long since I became a U.S. citizen (20 years to be exact) that I have no idea where (or even if) I have that certificate; I do have a valid U.S. passport however. Could I enter my passport number instead? Otherwise, could you tell me how I could retrieve my Naturalization Certificate number?