1. Tattersall, W. W. (1952).Lancet, 1, 202.
2. Weill-Hallé, B. (1925).Rév. de la Tuberc., 3, 164.
3. Philip, Sir R. (1937).Collected Papers on Tuberculosis. London.
4. Ministry of Health (1950).Ann. Rep. Chief Med. Offr. London.
5. Ryle, J. A. (1947).Lancet, 1, 1.