1. Beale, L. S. 1860. Examination of sputum from a case of cancer of the pharynx and adjacent parts. Arch. Med., 2, 44.
2. Dudgeon, L. S., Wrigley, C. H. 1935. On the demonstration of particles of malignant growth in the sputum by means of the wet film method. J. Laryng., 50, 752–763.
3. Duguid, H. L. D., Huish, D. W. 1963. Clinical evaluation of cytodiagnosis in bronchial carcinoma. Brit. med. J. 2, 287–291.
4. Erozan, Y. S., Frost, J. K. 1970. Cytopathological diagnosis of cancer in pulmonary material. A critical histopathological correlation. Acta. Cytol. (Philad.) 14, 560–565.
5. Frenzel, H. and Papageorgiou, A. 1964. Malignant cells in the sputum in coin lesions of the lung. German med. Mth., 9, 1–10.