@article{CMH_1980__55_139841,
     author = {Beno Eckmann and Heinz M\"uller},
     title = {Poincar\'e duality groups of dimension two.},
     journal = {Commentarii mathematici Helvetici},
     pages = {510--520},
     publisher = {mathdoc},
     volume = {55},
     year = {1980},
     zbl = {0458.20048},
     url = {http://geodesic.mathdoc.fr/item/CMH_1980__55_139841/}
}