Complex sentence: The first known sighting of Ellef Ringnes Island was in 1901 by a sledging party consisting of Gunerius Isachsen and Sverre Hassel, members of the Second Norwegian Arctic Expedition of 1898--1902, which was under the command of Otto Sverdrup.
Split into simpler sentences: The first known sighting of Ellef Ringnes Island was in 1901 by a sledging party consisting of Gunerius Isachsen and Sverre Hassel. Members of the Second Norwegian Arctic Expedition of 1898--1902, which was under the command of Otto Sverdrup.