@article{10_4064_cm_8_2_223_224,
     author = {A. Wallace},
     title = {Problems on semigroups},
     journal = {Colloquium Mathematicum},
     pages = {223--224},
     publisher = {mathdoc},
     volume = {8},
     number = {2},
     year = {1961},
     doi = {10.4064/cm-8-2-223-224},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-8-2-223-224/}
}