1. Philippe, R. J., and Hackney, E. J., Tobacco Science, 3, 139 (1959).
2. Haagen-Smit, A. J., Brunelle, M. F., and Hara, J., Amer. Med. Assoc. Arch. Indust. Health, 20, 399 (1959).
3. Bokhoven, C., and Niessen, H. J., Nature, 192, 458 (1961).
4. Tada, O., Rep. Inst. Science of Labour (Japan), No. 60, 7 (1962).
5. Gray, E. LeB., Amer. Med. Assoc. Arch. Indust. Health, 19, 479 (1959).