Extended Theories of Gravitation - Structure of Spacetime and Fundamental Principles of Physics, following Ehlers-Pirani-Schild FrameworkLorenzo Fatibene, Marco Ferraris, Mauro Francaviglia and Guido MagnanoEPJ Web of Conferences, 58 (2013) 02002DOI: https://doi.org/10.1051/epjconf/20135802002