1. INNOTRACK: Concluding Technical Reporthttp://www.innotrack.net/IMG/pdf/innotrack_concl_20techn_report_lowres.pdf
2. Modern Railway Trackhttp://www.esveld.com/MRT_Selection.pdf
3. Track Compendium: Formation, Permanent Way, Maintenance, Economicshttp://www.eurailpress.de/leseprobe/148/download/magazine.pdf
4. Track Geotechnology and Substructure Management;Selig,1994
5. The application of time domain ground penetrating radar to evaluate railway track ballast;Gallagher;NDT E Int,1999