@article{GDZPPN002231662, title = {The sigma-core of a cooperative game.}, journal = {Manuscripta mathematica}, volume = {70}, year = {1991}, pages = {247-254}, zbl = {0737.90081}, url = {http://dml.mathdoc.fr/item/GDZPPN002231662} }
Parker, June M. The sigma-core of a cooperative game.. Manuscripta mathematica, Tome 70 (1991) pp. 247-254. http://gdmltest.u-ga.fr/item/GDZPPN002231662/