113301document4395610.1016@0040-1625(90)90071-3.pdfapplication/pdf7db4a599a509a726a81caeaf5a899d99MD524900992016-03-21 09:33:15https://pure.iiasa.ac.at/id/eprint/3364/1/10.1016%400040-1625%2890%2990071-3.pdf