<r>Thanks Ev, that's the kind of models i was looking for.. found a paper on FEER (<URL url="http://www.ecomod.net/conferences/ecomod2003/ecomod2003_papers/piscitelli.pdf"><LINK_TEXT text="http://www.ecomod.net/conferences/ecomo ... itelli.pdf">http://www.ecomod.net/conferences/ecomod2003/ecomod2003...