F.G. Russo, Generalized $FC$-groups in finitary groups, preprint, http://www.fedoa.unina.it/1305/

F.G.Russo, On the connectivity of the Sylow graph of a finite group, Preprint

E. Khamseh, M.R.R. Moghaddam, F.G. Russo and F. Saeedi, Some remarks on elements with r-th roots in finite groups, Preprint