@article{PIM_1991_N_S_50_64_a9,
     author = {Stojan Bogdanovi\'c and Miroslav \'Ciri\'c},
     title = {Tight {Semigroups}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {71 },
     publisher = {mathdoc},
     volume = {_N_S_50},
     number = {64},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PIM_1991_N_S_50_64_a9/}
}