@article{700807,
title = {Ramification systems and spaces of ultrafilters},
booktitle = {General Topology and its Relations to Modern Analysis and Algebra},
series = {GDML\_Books},
publisher = {Academia Publishing House of the Czechoslovak Academy of Sciences},
address = {Praha},
year = {1972},
pages = {333-333},
mrnumber = {MR0351816},
url = {http://dml.mathdoc.fr/item/700807}
}
Negrepontis, S. Ramification systems and spaces of ultrafilters, dans General Topology and its Relations to Modern Analysis and Algebra, GDML_Books, (1972), p. 333. http://gdmltest.u-ga.fr/item/700807/