California Code, Streets and Highways Code - SHC § 8008

Proof of publication of any notice required by this part shall be made by affidavit, as provided in the Code of Civil Procedure, and proof of the posting of any such notice shall be made by the affidavit of the person posting the notice, setting forth the facts regarding such posting.

Any officer who is required by this part to have any notice published or posted shall obtain and file in his office the affidavits in proof thereof but his failure so to do shall not affect the validity of any proceedings under this part. Any such affidavit so filed shall be prima facie evidence of the facts therein stated regarding such publication or posting.