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2. Hippocratic writings,1978
3. Finger clubbing: Validity as a physical sign;Pyke;Lancet,1954
4. Quantitation of digital clubbing in children;Waring;Am Rev Respir Dis,1971
5. Correlation between digital clubbing and pulmonary function in cystic fibrosis;Nakamura;Pediatr Pulmonol,2002