@article{10_2140_agt_2013_13_625,
     author = {Sagave, Steffen and Schlichtkrull, Christian},
     title = {Group completion and units in {I-spaces}},
     journal = {Algebraic and Geometric Topology},
     pages = {625--686},
     year = {2013},
     volume = {13},
     number = {2},
     doi = {10.2140/agt.2013.13.625},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2013.13.625/}
}