Drysdale, Russell; Zanchetta, Giovanni; Hellstrom, John; Maas, Roland; Fallick, Anthony; Pickett, Matthew; Cartwright, Ian; Piccini, Leonardo (2006). "Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone". Geology. 34 (2): 101. Bibcode:2006Geo....34..101D. doi:10.1130/G22103.1.
Drysdale, Russell; Zanchetta, Giovanni; Hellstrom, John; Maas, Roland; Fallick, Anthony; Pickett, Matthew; Cartwright, Ian; Piccini, Leonardo (2006). "Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone". Geology. 34 (2): 101. Bibcode:2006Geo....34..101D. doi:10.1130/G22103.1.