@article{700843,
     title = {The space $\beta N$ and the continuum hypothesis},
     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 = {1967},
     pages = {144-146},
     mrnumber = {MR0233334},
     zbl = {0211.54605},
     url = {http://dml.mathdoc.fr/item/700843}
}

Gillman, L. The space $\beta N$ and the continuum hypothesis, dans General Topology and its Relations to Modern Analysis and Algebra, GDML_Books,  (1967), pp. 144-146. http://gdmltest.u-ga.fr/item/700843/