@article{SF_1985__32_134786,
     author = {W. Ruppert},
     title = {On weakly almost periodic sets.},
     journal = {Semigroup forum},
     pages = {267--282},
     year = {1985},
     volume = {32},
     zbl = {0569.22001},
     url = {http://geodesic.mathdoc.fr/item/SF_1985__32_134786/}
}