For an –component string link, the Milnor’s concordance invariant is defined for each sequence . Let denote the maximum number of times that any index appears. We show that two string links are equivalent up to self –moves and concordance if and only if their Milnor invariants coincide for all sequences with .
"Classification of string links up to self delta-moves and concordance." Algebr. Geom. Topol. 9 (1) 265 - 275, 2009. https://doi.org/10.2140/agt.2009.9.265