NOVIKS, Godfrīds. VIDES KOMPLEKSIE KRITĒRIJI UN INDIKATORI. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference, Rezekne, Latvia, v. 1, p. 125–132, 1999. DOI: 10.17770/etr1999vol1.1892. Disponível em: https://journals.rta.lv/index.php/ETR/article/view/1892.. Acesso em: 8 may. 2024.