1. Double Exposure Flat Plate Collector;Souka;Solar Energy,1965
2. Evaluation of Flat-Plate Solar Collector;Hoyte,1955
3. “Intensity of Direct Solar Radiation Normal to Sun'sRays at 30 Degrees North Latitude for Atmospheric Clearness Number of Unity”, ASHAE trans., 64 p. 64.
4. Incidence of Diffuse Sky Radiation During Clear Days;Threlkeld,1962