@article{10_4064_fm_112_3_165_170,
     author = {Andrzej Pelc},
     title = {Ideals on the real line and {Ulam's} problem},
     journal = {Fundamenta Mathematicae},
     pages = {165--170},
     publisher = {mathdoc},
     volume = {112},
     number = {3},
     year = {1981},
     doi = {10.4064/fm-112-3-165-170},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-112-3-165-170/}
}