Luis F. Romero Siham Tabik Jesús M. Vías Emilio L. Zapata Fast clear-sky solar irradiation computation for very large digital elevation models. 800-808 2008 178 Computer Physics Communications 11 http://dx.doi.org/10.1016/j.cpc.2008.01.048 db/journals/cphysics/cphysics178.html#RomeroTVZ08