Observations of Core Structure in Extensive Air Showers of 1015 - 1016 eV Hazen, W. E. ; Hodson, A. L. ; Keller, O. A. ; Green, B. R. ; Kass, J. R. Abstract Publication: International Cosmic Ray Conference Pub Date: August 1975 Bibcode: 1975ICRC....8.2984H