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- Bakker, J. (author), Vossepoel, F.C. (author), Kraa, A.R. (author), Broomhead, M.J. (author), van Vliet, L.D. (author), van Luipen, J.J.W. (author), Cremers, G. (author), Sprenger, M.L.M. (author), Frenken, G.W.R. (author), Punt, P.C. (author) report 1993