@article{10_4064_fm175_3_2,
     author = {Greg Hjorth},
     title = {The isomorphism relation on countable torsion free
 abelian groups},
     journal = {Fundamenta Mathematicae},
     pages = {241--257},
     publisher = {mathdoc},
     volume = {175},
     number = {3},
     year = {2002},
     doi = {10.4064/fm175-3-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm175-3-2/}
}