@article{HHA_2007_9_2_a4,
     author = {John C. Baez and Alissa S. Crans and Urs Schreiber and Danny Stevenson},
     title = {From loop groups to 2-groups},
     journal = {Homology, homotopy, and applications},
     pages = {101--135},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {2007},
     doi = {10.4310/HHA.2007.v9.n2.a4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4310/HHA.2007.v9.n2.a4/}
}