TY  - JOUR
AU  - N. Hindman
TI  - Strongly summable ultrafilters on N and small maximal subgroups of ßN.
JO  - Semigroup forum
PY  - 1991
SP  - 63
EP  - 76
VL  - 42
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1991__42_3_135065/
ID  - SF_1991__42_3_135065
ER  -