1\begin{thebibliography}{KFM08}
2
3\bibitem[KFM08]{MR2441256}
4L.~H. Kauffman and J.~Faria~Martins.
5\newblock Invariants of welded virtual knots via crossed module invariants of
6  knotted surfaces.
7\newblock {\em Compos. Math.}, 144(4):1046--1080, 2008.
8
9\bibitem[Kso00]{ksontini}
10R.~Ksontini.
11\newblock {\em Proprietes homotopiques du complexe de Quillen du groupe
12  symetrique}.
13\newblock These de doctorat, Universitet de Lausanne, 2000.
14
15\bibitem[Sat00]{MR1758871}
16S.~Satoh.
17\newblock Virtual knot presentation of ribbon torus-knots.
18\newblock {\em J. Knot Theory Ramifications}, 9(4):531--542, 2000.
19
20\end{thebibliography}
21