An approach to homotopy classification of links

Source abstract

A reformulation and refinement of the μ ¯ \overline \mu -invariants of Milnor are used to give a homotopy classification of 4 4 component links and suggest a possible general homotopy classification. The main idea is to use the (reduced) group of a link and its "geometric" automorphisms to define the precise indeterminacy of these invariants.