Trofimuk, A. A., and D. V. Gritsuk. “The Derived $p$-Length of a $p$-Solvable Group With Bounded Indices of Fitting $p$-Subgroups in Its Normal Closures”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 72, no. 3, Mar. 2020, pp. 366-70, doi:10.37863/umzh.v72i3.629.