Affiliation: | (1) Department of Mathematics, University of Manitoba, Winnipeg MN, R3T 2N2, Canada, e-mail: gratzer@cc.umanitoba.ca, URL: http://server.math.umanitoba.ca/homepages/gratzer.html/, CA;(2) C.N.R.S., Université de Caen, Campus II, Département de Mathématiques, B.P. 5186, 14032 Caen Cedex, France, e-mail: wehrung@math.unicaen.fr, URL: http://www.math.unicaen.fr/~wehrung, FR |