Cal. Pub. Res. Code § 5504

A petition may consist of any number of separate instruments, all of which together shall constitute one petition. Each instrument shall contain the affidavit of the person who circulated it, certifying that each signature is the true signature of the person whose name it purports to be. Every elector signing the petition shall write his address opposite his signature. The clerk of the board of supervisors of the county having the largest area within the proposed district, shall check and verify the signatures to the petition and certify the result of the examination to the board of supervisors.