In: M.B.A. van Asselt, J. Rotmans, S.C.H. Greeuw (eds); Puzzle-Solving for Policy: A Provisional Handbook for Integrated Assessment; Proceedings of the Advanced Summer Course, 30 August - 17 September 1999, Maastricht, Netherlands, International Centre for Integrative Studies (ICIS) pp.166-190 (2001)