1. Free groups and handlebodies;Andrews;Proc. Am. Math. Soc.,1965
2. Ribbon knots and ribbon discs;Asano;Osaka J. Math.,1981
3. A geometric approach to homology theory;Buoncristiano,1976
4. The topology of four-dimensional manifolds;Freedman;J. Diff. Geom.,1982
5. Ribbon concordance of knots in the 3-sphere;Gordon;Math. Ann.,1981