C. @aa and D. B8, A8 ::? 8@= :BB =?: ;8B ;?, =D: :AD :BA ??A 8; := 8B =: ;@ @; CC @D B8 8=8 8= 2 8=B CA :=? :@@ =8D @A@ =8=, pp.8-88

+. :. and =. Aa, ?D =DD 8D?D 8DAD =?@ 8?:@ ;; !,- :@D ;A :CA ;88 8CB ?DC ?A8 :;? BD@ ;= ( ,+ =A 8: ?C @B :A C? 88? ;C 8?= ;? &1 8@? A 8A: 8C? 8D? ;DD, 8C;C @8 U ;A: := ;C@ BA= 8A= 8D=B 8:=@ 8CB 8=== @: % :C=

=. A@, A 8:= ;D @8 C8 88; C= :DA =AD: !3 ,J :K 8D: @ 8DB 8: B :D 8D

=. =d, C ?8 ?8 ?, p.8
URL : https://hal.archives-ouvertes.fr/hal-00010407

. Dd=-!, 8;: 88? 88? ?8D; !,3 B: : B= BD BD ?8D= !, ?A ?A ?D ?D ?:D8 F 3 J :K 88@ A 8, ?=D: !, @8 ; @= @: @: ?=D; U+ 8D@, pp.8-8