Map of oil shale mining history in EstoniaValgma, Ingo5th International Mining History Congress : 12-15 September 2000, Milos Island - Greece : book of abstracts2000 / p. 116-119 : ill

Map of oil shale mining history in EstoniaValgma, Ingo5th International Mining History Congress : 12-15 September 2000, Milos Island, Greece : book of proceedings2001 / p. 189-193 : ill