1. HEGGESTAD, H.E., INTERNATIONAL JOURNAL OF AIR AND WATER POLLUTION 8: 1 (1964).
2. HILL, A.C., PHYTOPATHOLOGY 51: 336 (1961).
3. LEDBETTER, M.C., CONTRIBUTIONS FROM BOYCE THOMPSON INSTITUTE 20: 225 (1959).
4. Ozone damage to tobacco in Canada;CANADIAN PLANT DISEASE SURVEY,1963
5. MILLER, P.M., PLANT DISEASE REPORTER 52: 730 (1968).