@inbook{WoRMS:SourceID:155450, author = {Mortensen, T.}, title = {The Danish Ingolf-Expedition 1895-1896. Vol. 4, No. 2. Echinoidea}, url = {http://www.archive.org/stream/danishingolfexpe42danirich#page/n7/mode/2up}, year = {1907} }