Hess, Stéphane (September 10, 2013). "Physik: Kriminelle Energie erwünscht"(PDF). "BILDUNG SCHWEIZ" (Education Switzerland). pp. 24–25. Archived from the original(PDF) on March 3, 2016. Retrieved April 21, 2018.
Hess, Stéphane (September 10, 2013). "Physik: Kriminelle Energie erwünscht"(PDF). "BILDUNG SCHWEIZ" (Education Switzerland). pp. 24–25. Archived from the original(PDF) on March 3, 2016. Retrieved April 21, 2018.