LANZ, Adrian et al. Criterion 3: Maintenance and encouragement of productive functions of forests (wood and non-wood). In State of Europe's forests 2020 [elektronický zdroj]. - Bratislava : Ministerial Conference on the Protection of Forests in Europe - Forest Europe, 2020, p. 88-108 [online]. Dostupné na internete: <https://foresteurope.org/wp-content/uploads/2016/08/SoEF_2020.pdf>