Hass, Joel; Lagarias, Jeffrey C.; Pippenger, Nicholas: The computational complexity of knot and link problems, Journal of the ACM 46(2), 185–211 (1999). Arxiv
Benjamin A. Burton, Maximal admissible faces and asymptotic bounds for the normal surface solution space, Journal of Combinatorial Theory, Series A, Band 118, 2011, S. 1410–1435, Arxiv