@article{10_4064_fm_107_3_225_235,
     author = {Jussi Ketonen},
     title = {Some combinatorial properties of ultrafilters},
     journal = {Fundamenta Mathematicae},
     pages = {225--235},
     publisher = {mathdoc},
     volume = {107},
     number = {3},
     year = {1980},
     doi = {10.4064/fm-107-3-225-235},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-107-3-225-235/}
}