Skromulis, Andris, and Juris Breidaks. “Effect of Environmental Factors on Air Ion Concentration”. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 2 (June 17, 2015): 274–279. Accessed May 6, 2024. https://journals.rta.lv/index.php/ETR/article/view/241.