Montanari, Alessandro; Hay, Richard L.; Alvarez, Walter; Asaro, Frank; Michel, Helen V.; Alvarez, Luis W.; Smit, Jan (1983): Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition. Geological Society of America (GSA), Boulder, CO, United States, Geology (Boulder), 11 (11), 668-671, georefid:1983-061203