I was told that a knot complement in $S^3$ is an Eilenberg-Mc Lane space.
And that it is quite easy to see this. However I am not able to find out why.
could you help? Thanks



knot complement
Papakyriakopoulos, C. D. On Dehn's lemma and the asphericity of knots. Ann. of Math. (2) 66 (1957), 1–26.


