Parabolic isometries of CAT(0) spaces and CAT(0) dimensions. Fujiwara, Koji, Shioya, Takashi, Yamagata, Saeko (2004) Algebraic & Geometric Topology
Poincaré duality groups of dimension two. Beno Eckmann, Heinz Müller (1980) Commentarii mathematici Helvetici
Poincaré duality groups of dimension two, II. Beno Eckmann, Peter Linnell (1983) Commentarii mathematici Helvetici
Products of Conjugacy Classes in a Free Group: a Counterexample. S.M. Gersten (1986) Mathematische Zeitschrift