1. Evidence-Based Physical Diagnosis;McGee,2001
2. Studies on cyanosis;Lundsgaard;J Exp Med,1919
3. Dorland's Pocket Medical Dictionary (abridged from Dorland's Illustrated Medical Dictionary),2001
4. Harrison's Principles of Internal Medicine;Kasper,2008
5. Clubbing of the digits;Marrie;Am J Med,2007