Grove, K., Verdiani, L., Wilking, B. and Ziller, W. (2009) “Non-negative curvature obstructions in cohomogeneity one and the Kervaire spheres ”, ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, 5(2), pp. 159-170. doi: 10.2422/2036-2145.2006.2.02.