Sys, C., Vanelslander, T., Ponnekeblom, G., & Crius Group, H. (2011). Future challenges for inland navigation: A scientific appraisal of the consequences of possible strategic and economic developments up to 2030. Brussels, Belgium: University Press Antwerp.

Sys, Christa., Thierry Vanelslander, Gentbrugge Ponnekeblom, and Hulshout Crius Group. Future Challenges for Inland Navigation: A Scientific Appraisal of the Consequences of Possible Strategic and Economic Developments Up to 2030. Brussels, Belgium: University Press Antwerp, 2011.

Sys, Christa., Thierry Vanelslander, Gentbrugge Ponnekeblom, and Hulshout Crius Group. Future Challenges for Inland Navigation: A Scientific Appraisal of the Consequences of Possible Strategic and Economic Developments Up to 2030. Brussels, Belgium: University Press Antwerp, 2011.