Strategem : a micro computer based management training game on energy-environment interactions : user manual / Dennis Meadows, Wouter Biesiot, Mark GeertsReport on the power system simulation model SCELEC / [Daan Dijk, Mark Geerts]The state of the art: drivepower / by Amory B. Lovins and others ; samenvatting (April 1989 edition) M. GeertsStrategem : a micro computer based management training game on energy-environment interactions : user manual / Wouter Biesiot, Mark Geerts