@article{CMH_1935__8_138658,
     author = {M. Plancherel},
     title = {Sur les syst\`emes isogonaux de courbes dont le rapport des courbures est constant.},
     journal = {Commentarii mathematici Helvetici},
     pages = {354--358},
     publisher = {mathdoc},
     volume = {8},
     year = {1935},
     zbl = {0014.13203},
     url = {http://geodesic.mathdoc.fr/item/CMH_1935__8_138658/}
}