Professor Alf Egeland. Olav Christian Bernhard Birkeland. Research group for Plasma and Space Physics, University of Oslo. [2009-11-26]. (原始内容存档于2010-03-30).
web.archive.org
Professor Alf Egeland. Olav Christian Bernhard Birkeland. Research group for Plasma and Space Physics, University of Oslo. [2009-11-26]. (原始内容存档于2010-03-30).