The Ground Level Enhancements of 1989SEP29 and 1989OCT22 Duldig, M. L. ; Cramp, J. L. ; Humble, J. E. ; Smart, D. F. ; Shea, M. A. ; Bieber, J. W. ; Evenson, P. ; Fenton, K. B. ; Fenton, A. G. ; Bendoricchio, M. B. M. Abstract Publication: Publications of the Astronomical Society of Australia Pub Date: 1993 DOI: 10.1017/S1323358000025698 Bibcode: 1993PASA...10..211D