Peter Cröniger (July 2007). "Aufziehen Kontrollieren Starten"(PDF) (in German). DHV. pp. 41–42. Archived(PDF) from the original on 9 December 2014. Retrieved 5 December 2014.
"2011 FFVL Member Accident Report"(PDF) (in French). French Federation of Free Flight (FFVL). Archived(PDF) from the original on 19 March 2012. Retrieved 18 January 2012.
"2011 FFVL Member Accident Report"(PDF) (in French). French Federation of Free Flight (FFVL). Archived(PDF) from the original on 19 March 2012. Retrieved 18 January 2012.
Peter Cröniger (July 2007). "Aufziehen Kontrollieren Starten"(PDF) (in German). DHV. pp. 41–42. Archived(PDF) from the original on 9 December 2014. Retrieved 5 December 2014.