Periodic soluble groups in which every subnormal subgroup has defect at most two (Q1061844)

Let \(B_ n\) denote the class of groups in which every subnormal subgroup has defect at most n. The main results of the paper are: Theorem 1, a soluble p-group in \({\mathfrak B}_ 2\) has derived length at most 4, and at most 3 if \(p\neq 2\); Theorem 2, a periodic soluble group in \({\mathfrak B}_ 2\) has derived length at most 10.