@article{SF_1980__21_134444,
     author = {D. Helmer},
     title = {Joint continuity of affine semigroup actions.},
     journal = {Semigroup forum},
     pages = {153--166},
     publisher = {mathdoc},
     volume = {21},
     year = {1980},
     zbl = {0447.22001},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__21_134444/}
}