Hazan, Elad; Safra, Shmuel; Schwartz, Oded (2006), "On the complexity of approximating k-set packing", Computational Complexity, 15 (1): 20–39, doi:10.1007/s00037-006-0205-6, MR2226068, S2CID1858087. See in particular p.21: "Maximum clique (and therefore also maximum independent set and maximum set packing) cannot be approximated to within unless NP ⊂ ZPP."
Neuwohner, Meike (2021). "An improved approximation algorithm for the maximum weight independent set problem in d-claw free graphs". In Bläser, Markus; Monmege, Benjamin (eds.). 38th International Symposium on Theoretical Aspects of Computer Science, STACS 2021, March 16–19, 2021, Saarbrücken, Germany (Virtual Conference). LIPIcs. Vol.187. Schloss Dagstuhl – Leibniz-Zentrum für Informatik. pp.53:1–53:20. arXiv:2106.03545. doi:10.4230/LIPICS.STACS.2021.53.
Hazan, Elad; Safra, Shmuel; Schwartz, Oded (2006), "On the complexity of approximating k-set packing", Computational Complexity, 15 (1): 20–39, doi:10.1007/s00037-006-0205-6, MR2226068, S2CID1858087. See in particular p.21: "Maximum clique (and therefore also maximum independent set and maximum set packing) cannot be approximated to within unless NP ⊂ ZPP."
Neuwohner, Meike (2021). "An improved approximation algorithm for the maximum weight independent set problem in d-claw free graphs". In Bläser, Markus; Monmege, Benjamin (eds.). 38th International Symposium on Theoretical Aspects of Computer Science, STACS 2021, March 16–19, 2021, Saarbrücken, Germany (Virtual Conference). LIPIcs. Vol.187. Schloss Dagstuhl – Leibniz-Zentrum für Informatik. pp.53:1–53:20. arXiv:2106.03545. doi:10.4230/LIPICS.STACS.2021.53.
Hazan, Elad; Safra, Shmuel; Schwartz, Oded (2006), "On the complexity of approximating k-set packing", Computational Complexity, 15 (1): 20–39, doi:10.1007/s00037-006-0205-6, MR2226068, S2CID1858087. See in particular p.21: "Maximum clique (and therefore also maximum independent set and maximum set packing) cannot be approximated to within unless NP ⊂ ZPP."