@article{SF_1974__9_134069,
     author = {K. Takizawa},
     title = {Notes on {{Oa}-bands} of groupoids.},
     journal = {Semigroup forum},
     pages = {155--158},
     publisher = {mathdoc},
     volume = {9},
     year = {1974},
     zbl = {0289.06018},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__9_134069/}
}