"Fredrik Engelstad" (بالنرويجية). Dept. of Sociology and Human Geography, University of Oslo. 20 Feb 2009. Archived from the original on 2009-06-07. Retrieved 2009-03-01.
"Fredrik Engelstad" (بالنرويجية). Dept. of Sociology and Human Geography, University of Oslo. 20 Feb 2009. Archived from the original on 2009-06-07. Retrieved 2009-03-01.