@article{10_4171_dm_178,
     author = {Jean-Louis Tu},
     title = {Non-Hausdorff groupoids, proper actions and $K$-theory},
     journal = {Documenta mathematica},
     pages = {565--597},
     year = {2004},
     volume = {9},
     doi = {10.4171/dm/178},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/178/}
}