@article{CMH_1932__4_138571,
     author = {Harald Bohr},
     title = {Ueber fastperiodische ebene {Bewegungen.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {51--64},
     publisher = {mathdoc},
     volume = {4},
     year = {1932},
     zbl = {0005.06304},
     url = {http://geodesic.mathdoc.fr/item/CMH_1932__4_138571/}
}