1. Arthropathy and liver disease;Whelton, M.J.;Br J Hosp Med; Hypertrophic hepatic osteoarthropathy. Clinical, roentgenologic, biochemical, hormonal and cardiorespiratory studies,1970
2. Clinical assessment of clubbing;Pyke, D.A.;Lancet,1954
3. Estimation of clubbing by analysis of the shadowgraph;Bentley, D.; Cline, J.;Br Med J,1970