1. Topological invariants of knots and links;Alexander;TAMS,1928
2. An enumeration of knots and links, and some of their algebraic properties;Conway,1970
3. Knot corbordism groups in codimension two;Levine;Comm. Math. Helv.,1969
4. An algebraic classification of some knots of codimension two;Levine;Comm. Math. Helv.,1970
5. Über das Geschlecht von Knoten;Seifert;Math. Ann.,1934