* Beno Eckmann, _Poincaré duality groups of dimension 2 are surface groups_, In: Combinatorial Group Theory and Topology. (AM-111), 1987, pp. 35-52, [JSTOR](https://www.jstor.org/stable/j.ctt1b9x2np.5), [Google Books][1].

Also available in: Mathematical Survey Lectures 1943–2004. Springer, Berlin, Heidelberg, 2006. https://doi.org/10.1007/978-3-540-33791-1_9



  [1]: http://books.google.com/books?id=zaLQFGI-1AoC&lpg=PA51&dq=poincare%2520duality%2520groups%2520of%2520dimension%2520two&pg=PA35#v=onepage&q&f=false