California Code of Civil Procedure 412.20

(a) Except as otherwise required by statute, a summons shall be directed to the defendant, signed by the clerk and issued under the seal of the court in which the action is pending, and it shall contain:

(1) The title of the court in which the action is pending.
(2) The names of the parties to the action.
(3) A direction that the defendant file with the court a written
pleading in response to the complaint within 30 days after summons is
served on him or her.
(4) A notice that, unless the defendant so responds, his or her
default will be entered upon application by the plaintiff, and the
plaintiff may apply to the court for the relief demanded in the
complaint, which could result in garnishment of wages, taking of
money or property, or other relief.
(5) The following statement in boldface type: “You may seek the
advice of an attorney in any matter connected with the complaint or
this summons. Such attorney should be consulted promptly so that your
pleading may be filed or entered within the time required by this
summons.”
(6) The following introductory legend at the top of the summons
above all other matter, in boldface type, in English and Spanish:
“Notice! You have been sued. The court may decide against you
without your being heard unless you respond within 30 days. Read
information below.”

(b) Each county may, by ordinance, require that the legend
contained in paragraph (6) of subdivision (a) be set forth in every
summons issued out of the courts of that county in any additional
foreign language, if the legend in the additional foreign language is
set forth in the summons in the same manner as required in that
paragraph.

(c) A summons in a form approved by the Judicial Council is deemed
to comply with this section.

Source.