Cal. Bus. & Prof. Code § 2406.5
(a) When a physician and surgeon, podiatrist, or other referring practitioner refers a patient to receive services by a physical therapist employed by a professional corporation as defined in Section 13401 of the Corporations Code, the referring practitioner shall comply with Article 6 (commencing with Section 650) of Chapter 1, and shall provide notice of the following to the patient, orally and in writing, in at least 14-point type and signed by the patient: