APA
International Society for Rock Mechanics, . (1991). Rock mechanics. 7th international congress, Aachen, 1991. Proceedings. Vol 1-3. Rotterdam: International Society for Rock Mechanics.
Chicago
International Society for Rock Mechanics, . 1991. Rock mechanics. 7th international congress, Aachen, 1991. Proceedings. Vol 1-3. Rotterdam: International Society for Rock Mechanics.
Harvard
International Society for Rock Mechanics, . (1991). Rock mechanics. 7th international congress, Aachen, 1991. Proceedings. Vol 1-3. Rotterdam: International Society for Rock Mechanics.
MLA
International Society for Rock Mechanics, . Rock mechanics. 7th international congress, Aachen, 1991. Proceedings. Vol 1-3. Rotterdam: International Society for Rock Mechanics. 1991.