22 CFR 50.20: Retention of nationality.

(a) Section 351(b) of the Immigration and Nationality Act. (1) A person who desires to claim U.S. nationality under the provisions of section 351(b) of the Immigration and Nationality Act must, within the time period specified in the statute, assert a claim to U.S. nationality and subscribe to an oath of allegiance before a diplomatic or consular officer.

(2) In addition, the person shall submit to the Department a statement reciting the person's identity and acquisition or derivation of U.S. nationality, the facts pertaining to the performance of any act which would otherwise have been expatriative, and his desire to retain his U.S. nationality.