@article{SIGMA_2013_9_a7,
     author = {Eugenio Bianchi and Frank Hellmann},
     title = {The {Construction} of {Spin} {Foam} {Vertex} {Amplitudes}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2013},
     volume = {9},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2013_9_a7/}
}