R Medicine (General)
RA Public aspects of medicine
RB Pathology
RC Internal medicine
RC 71 Lasers - Diagnostic Use
RC 78 Diagnosis, Radioscopic; Medical Radiology; Magnetic Resonance Imaging; Radiography, Medical; Radiologic
Technologists
RC 78.7 Diagnostic Imaging; Diagnostic Imaging Ultrasound; Radiographic Contrast Media; Tomography; Tomography, Emission;
Ultrasonic Imaging
RD Surgery
RE Ophthalmology
RF Otorhinolaryngology
RG Gynecology and obstetrics
RG 527 Ultrasonics in Obstetrics
RJ Pediatrics
RK Dentistry
RL Dermatology
RM Therapeutics. Pharmacology
RS Pharmacy and materia medica
RT Nursing
RV Botanic, Thomsonian, and eclectic medicine
RX Homeopathy
RZ Other systems of medicine