@article{10_4171_ggd_30,
     author = {Joan S. Birman and Volker Gebhardt and Juan Gonz\'alez-Meneses},
     title = {Conjugacy in {Garside} groups {II:} structure of the ultra summit set},
     journal = {Groups, geometry, and dynamics},
     pages = {13--61},
     year = {2008},
     volume = {2},
     number = {1},
     doi = {10.4171/ggd/30},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/30/}
}