California Code, Corporations Code - CORP § 193

(a) An affidavit signed by them under oath before an officer authorized by the laws of this state or of the place where it is executed to administer oaths, or

(b) A declaration in writing executed by them “under penalty of perjury” and stating the date and place (whether within or without this state) of execution.

Any affidavit sworn to without this state before a notary public or a judge or clerk of a court of record having an official seal need not be further authenticated.