O. Olsen

The piscatorial atlas of the North Sea, English and St. George's Channels, illustrating the fishing ports, boats, gear, species of fish (how, where, and when caught), and other information concerning fish and fisheries

O. Olsen, 1883 .

Large populations of the common toad Bufo bufo in Norway

D. Dolmen, S. Roth, O. Olsen, 2016 .

Roosts used by bats in late autumn and winter at northern latitudes in Norway

T. Michaelsen, K. Grimstad, O. Olsen, 2013, Folia Zoologica.