Webster, C.R., R.D. May, D.W. Toohey, L.M. Avallone, J.G. Anderson, P.A. Newman, L.R. Lait, M.R. Schoeberl, J.W. Elkins, and . Chan (1993), Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter, Science, 261, 1140-1143.