Iljins, U., I. Ziemelis, H. Putāns, A. Šķēle, and J. Navickas. 2006. “Optimization of the Parameters of Solar Water Heating System”. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 1 (June): 353-58. https://doi.org/10.17770/etr2003vol1.1994.