@article{MABA_1991_5_2_a0,
     author = {Shi Mingquan},
     title = {Some {Results} of the {\ensuremath{\pi}-Semigroups}},
     journal = {Mathematica balkanica},
     pages = {81},
     publisher = {mathdoc},
     volume = {5},
     number = {2},
     year = {1991},
     url = {http://geodesic.mathdoc.fr/item/MABA_1991_5_2_a0/}
}