112087document4395410.1016@0196-8904(92)90082-8.pdfapplication/pdf1c72873aa2a2e38367e3415c518cdd13MD57648632016-03-21 09:24:50https://pure.iiasa.ac.at/id/eprint/3593/1/10.1016%400196-8904%2892%2990082-8.pdf