by (Netherlands)M.Benson;by C.M.Schwarz; by (Netherlands)R.Kubo;by (USSR)L.D.Landau; by (Netherlands)B.L.Waerden;by (USSR)A.Yariv; by (Netherlands)P.J.Chen;by (USSR)A.S.Davydov; by (Netherlands)V.Ponec;by (USSR)L.Dobrzynski;