@article{10_4064_ap_24_3_327_330,
     author = {W. R. Utz},
     title = {Periodic solutions of $x" + f(x)x'^m + g(x) = 0$},
     journal = {Annales Polonici Mathematici},
     pages = {327--330},
     publisher = {mathdoc},
     volume = {24},
     number = {3},
     year = {1970},
     doi = {10.4064/ap-24-3-327-330},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-24-3-327-330/}
}