To be sure you have a thorough review of what has been done, got to Milnor’s original conjecture on mathscinet and to a few of the articles mentioned above and check who has cited them. This should bring you to everything that has been published.

To be sure you have a thorough review of what has been done, go to Milnor’s paper with the original conjecture on mathscinet and to a few of the articles mentioned above and check who has cited them. This should bring you to everything that has been published.