Hydropower or non-market values of nature : a contingent valuation study of Jägala Waterfalls, EstoniaEhrlich, Üllas; Reimann, MartRecent Researches in Energy, Environment, Devices, Systems, Communications and Computers : International Conference on Energy, Environment, Devices, Systems, Communications, Computers (EEDSCC'11) : Venice, Italy, March 8-10, 20112011 / p. 232-237 : ill The Narva waterfall and the technological solutions for harnessing its energyMägi, VahurProceedings of St.Petersburg IEEE Chapters. Vol. 12005 / p. 71-74 Uuring : ülikoolid arvutasid Jägala joa väärtuseks 157 miljonit krooni : [ka TTÜ vanemteaduri Üllas Ehrlichi arvamus]Jaagant, Urmas; Ehrlich, ÜllasEesti Päevaleht2009 / 16. apr., lk. 9 https://epl.delfi.ee/artikkel/51165424/uuring-ulikoolid-arvutasid-jagala-joa-vaartuseks-157-miljonit