@article{BMMS_2007_30_1_a6,
     author = {A. Abdollahi and F. Ashraf and S. M. Shaker},
     title = {The {Symmetric} {Group} of {Degree} {Six} can be {Covered} by 13 and no {Fewer} {Proper} {Subgroups}},
     journal = {Bulletin of the Malaysian Mathematical Society},
     year = {2007},
     volume = {30},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/BMMS_2007_30_1_a6/}
}