by (Federal Republic of Germany)B.Freund;by (United Kingdom)N.Wrigley...et al; by (Federal Republic of Germany)H.Weyl;by (United Kingdom)J.Foster...et al; by (Federal Republic of Germany)R.Hahn;by (United Kingdom)M.Patton...et al; by (Federal Republic of Germany)B.Bollobas; (United Kingdom)L.W.Beineke...et al; by (Federal Republic of Germany)B.R.Nag;by (United Kingdom)B.K.Ridley; by (Federal Republic of Germany)B.Zielonka;by (United Kingdom)S.Greenall; by (Federal Republic of Germany)B.R.Frieden;by (United Kingdom)A.D.Gordon; by (Federal Republic of Germany)D.Kuhne;by (United Kingdom)G.W.Hoffman; by (Federal Republic of Germany)G.Zumpe;by (United Kingdom)A.B.Tayler; by (Federal Republic of Germany)J.Haydn;by (United Kingdom)B.Bartok;