Cal. Elec. Code § 9206
Within 10 days after the date of publication or posting, or both, of the notice of intention and title and summary, the proponents shall file a copy of the notice and title and summary as published or posted together with an affidavit made by a representative of the newspaper in which the notice was published or, if the notice was posted, by a voter of the city, certifying to the fact of publication or posting.
If the notice and title and summary are both published and posted pursuant to subdivision (b) of Section 9205, the proponents shall file affidavits as required by this section made by a representative of the newspaper in which the notice was published certifying to the fact that the notice was published and by a voter of the city certifying to the fact that the notice was posted.
These affidavits, together with a copy of the notice of intention and title and summary, shall be filed with the elections official of the legislative body of the city in his or her office during normal office hours as posted.
Ca. Elec. Code § 9206