@book{UBHD-1475964, author={Ludvigsen, Rolf}, title={A trilobite zonation of Middle Ordovician rocks, southwestern District of Mackenzie}, publisher={Geological Survey of Canada}, address={Ottawa}, year={1979}, pages={98 S.}, language={eng}, isbn={0-660-10165-3 and 978-0-660-10165-1}, number={ARRAY(0x560579b54630)}, series={Bulletin / Geological Survey of Canada}, library={UB [Signatur: 79 S 203]}, }