German doctors are bound by the professional codes of their medical chambers. The code of the medical chamber of North Rhine says that where diagnosis and treatment require it, doctors must call in other doctors in good time, oder ihnen die Patientin oder den Patienten zur Fortsetzung der Behandlung zu überweisen, or refer the patient to them to continue the treatment. Patients know the result as the Überweisung, the referral slip from the family doctor to the specialist.