Track to '75 : plan for the future of NS in Dutch society in the years 1970-1975Annual ReportRail works in LeidenThe train to the 21st century : from plan to approachRail 21 : tracks to a new centuryThe future of the Dutch RailwaysJustification of constructions and estimates : contained in the note concerning the cost of completing the ring railroad at AmsterdamNote on the cost of completing the ring railroad at Amsterdam : consideration, design and cost estimate