#### Volume 5, issue 1 (2001)

 1 M M Cohen, A course in simple-homotopy theory, Graduate Texts in Mathematics 10, Springer (1973) MR0362320 2 M M Cohen, Whitehead torsion, group extensions, and Zeeman's conjecture in high dimensions, Topology 16 (1977) 79 MR0436155 3 M M Cohen, M Lustig, The conjugacy problem for Dehn twist automorphisms of free groups, Comment. Math. Helv. 74 (1999) 179 MR1691946 4 R Fenn, C Rourke, Klyachko's methods and the solution of equations over torsion-free groups, Enseign. Math. $(2)$ 42 (1996) 49 MR1395041 5 R Fenn, C Rourke, Characterisation of a class of equations with solutions over torsion-free groups, from: "The Epstein birthday schrift", Geom. Topol. Monogr. 1, Geom. Topol. Publ., Coventry (1998) 159 MR1668351 6 W Metzler, Über den Homotopietyp zweidimensionaler CW–Komplexe und Elementartransformationen bei Darstellungen von Gruppen durch Erzeugende und definierende Relationen, J. Reine Angew. Math. 285 (1976) 7 MR0440527 7 M A Kervaire, On higher dimensional knots, from: "Differential and Combinatorial Topology (A Symposium in Honor of Marston Morse)", Princeton Univ. Press (1965) 105 MR0178475 8 A A Klyachko, A funny property of sphere and equations over groups, Comm. Algebra 21 (1993) 2555 MR1218513 9 O S Rothaus, On the non-triviality of some group extensions given by generators and relations, Ann. Math. $(2)$ 106 (1977) 599 MR0467760 10 C P Rourke, B J Sanderson, Introduction to piecewise-linear topology, Springer Study Edition, Springer (1982) MR665919