23.67 G.Francia, A new collector of solar radiant energy – Theory and experimental verification, (United Nations Conference on New Sources of Energy - Solar, Energy, Wind Power and Geothermal Energy, 3 may 1961); (in allegato: disegni tecnici). Collector with three coaxial conical frusta wich, starting at a diameter of 3.20 m, concentrates the radiant energy on a beehive collector 0.80m in diameter at a theoretical concentration of 16:1.