Frijters, Ine D.; Leentvaar, Jan (2003). Rhine Case Study. Technical documents in hydrology, no. 17. Paris: UNESCO International Hydrological Programme, (Rep. No. SC/2003/WS/54). OCLC55974122.
Frijters, Ine D.; Leentvaar, Jan (2003). Rhine Case Study. Technical documents in hydrology, no. 17. Paris: UNESCO International Hydrological Programme, (Rep. No. SC/2003/WS/54). OCLC55974122.