@article{10_4064_cm95_1_9,
     author = {Nikos Frantzikinakis},
     title = {Additive functions
 modulo a countable subgroup of ${\Bbb R}$},
     journal = {Colloquium Mathematicum},
     pages = {117--122},
     publisher = {mathdoc},
     volume = {95},
     number = {1},
     year = {2003},
     doi = {10.4064/cm95-1-9},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm95-1-9/}
}