ALKAFF, A. MONTHLY AVERAGE DAILY INSOLATION AND OPTIMUM TILT ANGLE OF SOLAR COLLECTOR IN P.D.R. YEMEN Periodica Polytechnica Mechanical Engineering, [S. l.], v. 35, n. 3, p. 183–198, 1991. Disponível em: https://pp5.omikk.bme.hu/me/article/view/5597. Acesso em: 10 feb. 2025.