THORBERGSSON, Gudlaugur. Non-hyperbolic closed geodesics. MATHEMATICA SCANDINAVICA, [S. l.], v. 44, p. 135–148, 1979. DOI: 10.7146/math.scand.a-11799. Disponível em: https://tidsskrift.dk/math/article/view/11799. Acesso em: 14 aug. 2026.