1. Stephan Freudenstein. Research report No. 2466 of 19 September 2008 by Munich University of Technology, transport infrastructure engineering department and test laboratory, Univ. Prof. Dr.-Ing.
2. Günther Koller. RTR 2/2009 special report, The use of sleepers made of FFU synthetic wood in Europe.
3. Stephan Freudenstein. Research report No. 3017 of 8 July 2013 by Munich University of Technology, transport infrastructure engineering department and test laboratory, Univ. Prof. Dr.-Ing.