1. Eine Kennzeichnung der Torusknoten;Burde;Math. Z.,1966
2. Free products with amalgamation and 3-manifolds;Epstein;Proc. Am. math. Soc.,1961
3. Curves on 2-manifolds and isotopies;Epstein;Acta Math.,1966
4. The Theory of Groups;Kurosh,1956
5. The Theory of Groups;Kurosh,1960