All doctors who receive referrals from the SSN are affiliated with Sutter's network of care—members of the medical staff of Sutter-affiliated hospitals, affiliated medical groups, and independent practice associations that participate in clinical initiatives. Doctors do not pay a fee to be included in this referral service. If a physician ceases to fall within one of the categories noted, he/she would no longer be included in the SSN Referral Service. Referrals are reviewed under initial criteria such as insurance product restrictions, geographic proximity, capacity, equipment needed and first available appointment. SSN also applies patient preference criteria (for example, male, female, age, language, proximity to public transportation etc.).