The discovery of North America twenty years before Columbus,
by Sofus Larsen.
APA Citation
Larsen, S. (1925). The discovery of North America twenty years before Columbus. Copenhagen: Levin & Munksgaard; [etc., etc.].
MLA Citation
Larsen, Sofus, 1855-1938. The Discovery of North America Twenty Years Before Columbus. Copenhagen: Levin & Munksgaard; [etc., etc.], 1925.
Warning: These citations may not always be complete (especially for serials).