@article{10_4064_fm_131_3_215_221,
     author = {Jan Pelant and Petr Simon and Jerry Vaughan},
     title = {The smallest number of free closed filters},
     journal = {Fundamenta Mathematicae},
     pages = {215--221},
     publisher = {mathdoc},
     volume = {131},
     number = {3},
     year = {1988},
     doi = {10.4064/fm-131-3-215-221},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-131-3-215-221/}
}