@article{SF_1976__12_134178,
     author = {K. Sigmon and H.-T. Hu},
     title = {Continuously factorable groupoids.},
     journal = {Semigroup forum},
     pages = {251--264},
     publisher = {mathdoc},
     volume = {12},
     year = {1976},
     zbl = {0327.22002},
     url = {http://geodesic.mathdoc.fr/item/SF_1976__12_134178/}
}