2009 California Code of Civil Procedure - Section 1297.71-1297.72 :: Article 1. Definition And Form Of Arbitration Agreements

1297.71.  An "arbitration agreement" is an agreement by the parties
to submit to arbitration all or certain disputes which have arisen or
which may arise between them in respect of a defined legal
relationship, whether contractual or not. An arbitration agreement
may be in the form of an arbitration clause in a contract or in the
form of a separate agreement.

1297.72.  An arbitration agreement shall be in writing. An agreement
is in writing if it is contained in a document signed by the parties
or in an exchange of letters, telex, telegrams, or other means of
telecommunication which provide a record of this agreement, or in an
exchange of statements of claim and defense in which the existence of
an agreement is alleged by one party and not denied by another. The
reference in a contract to a document containing an arbitration
clause constitutes an arbitration agreement provided that the
contract is in writing and the reference is such as to make that
clause part of the contract.