(挪威语). Saga of Sigurd the Crusader and his brothers Eystein and Olaf, chapter 18. Saga of Sigurd the Crusader and his brothers Eystein and Olaf, chapter
(原始内容存档于2014-02-01). Official State visit ofNorway (Photo of Order of State and Order of St. Olaf). Presidency of Republic of Turkey. 2013-05-11 [2013-11-11].
Miltenburg, Olaf. TU Delft onthult Hyperloop-ontwerp - Vervoermiddel van de toekomst [TU Delft unveils Hyperloop design - Means of transport of the future]