• Detection of mine collapses with seismic methods - a case study from EstoniaSoosalu, Heidi Elisabet; Valgma, IngoInternational Oil Shale Symposium : Tallinn, Estonia, June 8-11, 2009 : future energy solutions : come and share your vision!2009 / p. 101-102 http://www.ester.ee/record=b4775098*est