Comparison of TOMS and AVHRR volcanic ash retrievals from the August 1992 eruption of Mt. Spurr - Krotkov, N.A.; Torres, O.; Seftor, C.; Krueger, A.J.; Kostinski, A.; Rose Jr., William; Bluth, G.J.S.; Schneider, D.; Schaefer, S.J. (Geophysical Research Letters, 1999)