California Code, Code of Civil Procedure - CCP § 751.12

At any time within three months after the first publication of the summons, or such further time not exceeding 30 days as the court for good cause may grant, any person having or claiming any estate, right, title, or interest in or to, or lien upon, all or any part of the property may appear and make himself a party to the action by pleading to the complaint. All answers must be verified and must specifically set forth the estate, right, title, interest, or lien so claimed.