@article{SF_1985__32_134787,
     author = {N. Hindman},
     title = {The minimal ideals of a multiplicative and additive subsemigroup of {{\ss}N.}},
     journal = {Semigroup forum},
     pages = {283--292},
     publisher = {mathdoc},
     volume = {32},
     year = {1985},
     zbl = {0576.22006},
     url = {http://geodesic.mathdoc.fr/item/SF_1985__32_134787/}
}