@article{CMH_1974__49_139594,
     author = {Robert Bieri and Benno Eckmann},
     title = {Amalgamated {Free} {Products} of {Groups} and {Homological} {Duality}},
     journal = {Commentarii mathematici Helvetici},
     pages = {460--478},
     publisher = {mathdoc},
     volume = {49},
     year = {1974},
     zbl = {0304.20034},
     url = {http://geodesic.mathdoc.fr/item/CMH_1974__49_139594/}
}