References
- Vachkov, K.; Galcheva, P. Chemistry and preservation of the natural environment, Shumen University "Bishop Konstantin Preslavski", Shumen, 2012.
- Kirilov, M.; Neykov, G.; Kolarova, Z. Chemistry and environmental protection for the 9th grade, Compulsory preparation, Bulvest 2000, Sofia, 2001.
- Zaharinov, B., Naydenov, Y. Environmental monitoring, NBU, Sofia, 2015.
- https://ucha.se/watch/7647/prirodnoresursen-potentsial-prirodopolzvane-vidove-prirodni-resursi, 2018.
- Angelova, R., Kabasanova, M. General teaching methodology in biology. St Kliment Ohridski University Publishing House, Sofia, 1992.
- Vasileva-Tсankova, R. Possible semiotic approaches in teaching and learning chemical symbols in seventh and eighth grade, Monograph, Libra Scorp Publishing House, Burgas, 2022.
- Vasileva-Tсankova, R. Modern methods, approaches and technologies of teaching in Chemistry and environmental protection, Monograph, Libra Scorp Publishing House, Burgas, 2022.
- Vakleva, Z. Contemporary aspects of environmental education. Anniversary scientific conference on ecology (Collection of reports), Editors: Iliana Velcheva, Angel Tsekov, Plovdiv, 2008, 410–419.
- Kostova, Z. Interactive forms in environmental education, Biology, Ecology and Biotechnology, 2001, 5. Dimova, D. Education for sustainable development. Theoretical and methodological aspects, RITT, Silistra, 2001.