Cal. Elec. Code § 9022

(a) Each section shall have attached thereto the declaration of the person soliciting the signatures setting forth the information required by Section 104 and stating that the circulator is a voter or is qualified to register to vote in the state.

(b) The circulator shall certify to the content of the declaration as to its truth and correctness, under penalty of perjury under the laws of the State of California, with the signature of his or her name at length, including given name and middle name or initial. The circulator shall state the date and the place of execution on the declaration immediately preceding his or her signature.

Another declaration thereto may not be required.

Petitions so verified shall be prima facie evidence that the signatures thereon are genuine and that the persons signing are qualified voters. Unless and until otherwise proven upon official investigation, it shall be presumed that the petition presented contains the signatures of the requisite number of qualified voters.