@article{SF_1984__30_134703,
     author = {P. Milnes and N. Hindman},
     title = {The ideal structure of {XX.}},
     journal = {Semigroup forum},
     pages = {41--52},
     publisher = {mathdoc},
     volume = {30},
     year = {1984},
     zbl = {0532.22004},
     url = {http://geodesic.mathdoc.fr/item/SF_1984__30_134703/}
}