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\item ({\sl with A. Lucchini and M.$\,$C. Tamburini}) Hurwitz groups of large rank. {\sl J. London Math. Soc. \rm(2) {\bf 61}} (2000), 81--92.
\item On abstract and profinite just infinite groups. Chapter 5 in {\sl New horizons in pro-$p$ groups} (Birk\-ha\"user, 2000).
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\item ({\sl with R.$\,$I. Grigorchuk}) A structural property concerning abstract commensurability of subgroups. {\sl J. London Math. Soc. \rm(2) {\bf 68}} (2003), 671--682.
\item ({\sl with R.$\,$I. Grigorchuk}) The uniqueness of the actions of certain branch groups on rooted trees. {\sl Geom. Dedicata {\bf 100}} (2003), 103--116.
\item On exponential growth and uniformly exponential growth for groups. {\sl Invent. Math. {\bf155}} (2004), 287--303.
\item On growth of groups with few relators. {\sl Bull. London Math. Soc. {\bf 36}} (2004), 1--2.
\item Structure theory for branch groups. In {\sl Geometric and Homological Topics in Group Theory} (Cambridge University Press), to appear.
%\item A short primer on profinite groups. To appear.
\item First-order characterization of the radical of a finite group. {\sl J. Symbolic Logic}, to appear.
\item Linear groups with many $2$-generator soluble subgroups. {\sl Bull. London Math. Soc.}, to appear.
\item Characterization of the soluble radical by a sequence of words. {\sl J. Algebra}, to appear. \end{itemize}

{\bf Popular article} The glass bead game. {\sl Math. Intelligencer {\bf 19}} (1997), no. 2, 23--25.