@article{GDZPPN002422654, title = {Subgroups of Finite Index in Profinite Groups.}, journal = {Mathematische Zeitschrift}, volume = {166}, year = {1979}, pages = {71-76}, zbl = {0394.20020}, url = {http://dml.mathdoc.fr/item/GDZPPN002422654} }
Hartley, Brian. Subgroups of Finite Index in Profinite Groups.. Mathematische Zeitschrift, Tome 166 (1979) pp. 71-76. http://gdmltest.u-ga.fr/item/GDZPPN002422654/