On groups whose every proper subgroup is a Bn -group

Abstract

Let G be a group in which every proper subgroup is a B n -group. Also, [ G , X ] has finite exponent, foran x e G . B n -group denotes the class of ali group in which no subnormal subgroups has defect exceeding n , where n is a natural nutnber. It is proved that the groups are soluble and Fitting groups.