@article{GDZPPN002363828, title = {Groups as the union of proper subgroups.}, journal = {Mathematica Scandinavica}, volume = {81}, year = {1998}, pages = {191-198}, zbl = {0905.20014}, url = {http://dml.mathdoc.fr/item/GDZPPN002363828} }
Tomkinson, M.J. Groups as the union of proper subgroups.. Mathematica Scandinavica, Tome 81 (1998) pp. 191-198. http://gdmltest.u-ga.fr/item/GDZPPN002363828/