@article{10_4064_fm196_3_1,
     author = {Saharon Shelah and Juris Stepr\={a}ns},
     title = {Possible cardinalities of maximal
abelian subgroups of quotients of permutation groups of the integers},
     journal = {Fundamenta Mathematicae},
     pages = {197--235},
     publisher = {mathdoc},
     volume = {196},
     number = {3},
     year = {2007},
     doi = {10.4064/fm196-3-1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm196-3-1/}
}