@article{10_4153_CJM_1974_146_6,
     author = {Arad, Zvi},
     title = {A {Characteristic} {Subgroup} of {\ensuremath{\pi}-Stable} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {1509--1514},
     year = {1974},
     volume = {26},
     number = {6},
     doi = {10.4153/CJM-1974-146-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1974-146-6/}
}