Erratic boulders as natural monuments in Estonia

Kirs, J., Pirrus, E. Erratic boulders as natural monuments in Estonia // ProGeo '97 in Estonia : proceedings : the Second General Assembly of the European Association for the Conservation of the Geological Heritage : scientific conference : proceedings, Tallinn - Lahemaa National Park, Estonia, June 2-4, 1997. Tallinn, 1998. p. 31-34: ill.