Giulio, Andrea Di; Andrea Ceriani; Emanuele Ghia; Francesco Zucca (2003). "Composition of modern stream sands derived from sedimentary source rocks in a temperate climate (Northern Apennines, Italy)". Sedimentary Geology. 158 (s 1–2): 145–161. doi:10.1016/S0037-0738(02)00264-6.
Busaccaa, Alan; Mauro Cremaschi (1998). "The role of time versus climate in the formation of deep soils of the Apennine fringe of the Po Valley, Italy". Quaternary International. 51–52: 95–107. doi:10.1016/S1040-6182(97)00036-0.
"Geography of the Trebbia Valley" (in Italian and English). Associazione Pro Loco Gorreto. 2006. Archived from the original on November 20, 2008. Retrieved 2 April 2009.