@article{GDZPPN002051214, title = {Ueber fastperiodische ebene Bewegungen.}, journal = {Commentarii mathematici Helvetici}, volume = {4}, year = {1932}, pages = {51-64}, zbl = {0005.06304}, url = {http://dml.mathdoc.fr/item/GDZPPN002051214} }
Bohr, Harald. Ueber fastperiodische ebene Bewegungen.. Commentarii mathematici Helvetici, Tome 4 (1932) pp. 51-64. http://gdmltest.u-ga.fr/item/GDZPPN002051214/