much simpler and rigorous way. That's all, these results now can be used in future models. All the best, Tibor Tibor ANTAL =el: +44 1316-517-672 School of Mathematics, Edinburgh University http://www.maths.ed.ac.ukhant=1<http://www.maths.ed.ac.ukhantal> JCMB5403 The University of Edinburgh is a charitable body, r