Tracing prehistoric past human routes in the Pyrenees: new data about chert procurement at Montlleó open-air site (Prats i Sansor, Spain) - Marta Sánchez de la Torre; Xavier Mangado; François-Xavier Le Bourdonnec; Bernard Gratuze; Mathieu Langlais; Oriol Mercadal; Josep Maria Fullola (UISPP Journal, 2021)