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2. F. Bonahon and L. Siebenmann, New geometric splittings of classical knots (to appear).
3. An enumeration of knots and links, and some of their algebraic properties;Conway, J. H.,1970
4. Presentations of the trefoil group;Dunwoody, M. J.;Canad. Math. Bull.,1973
5. W. Jaco, Lectures on 3-manifolds topology, CBMS Regional Conf. Ser. in Math., no. 43, Amer. Math. Soc., Providence, R. I., 1979.