Matisovs, Ivars. “ECOLOGICAL EXPEDITION AS EFFECTIVE FORM OF ENVIRONMENTAL RESEARCH AND ECOLOGICAL EDUCATION”. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 1 (June 23, 2007): 254–261. Accessed May 3, 2024. https://journals.rta.lv/index.php/ETR/article/view/1730.