1. Vandegrift, A.E., Shannon, L.J., Sallee, E.E. et al (1971) J. Air Pollut. Control Assoc, 21, 321–8.
2. Warren Spring Laboratory (1966) National Survey of Smoke and Sulphur Dioxide Instruction Manual, Ministry of Technology, London.
3. Whatman Leaflet AP-69, W. and R. Balston Ltd, Maidstone, Kent, England.
4. Spurny, K., Lodge, J.P. (1968) Staub-Reinhalt. Luft, 28, 1–10.
5. Spurny, K.R., Lodge, J.P., Frank, E.R., Sheesley, D.C. (1969) Environ. Sci. Technol., 3, 453–64.