@article{CMH_1959__33_139177,
     author = {Y.W. Chen},
     title = {HOELDER continuity and initial value problems of mixed type differential equations.},
     journal = {Commentarii mathematici Helvetici},
     pages = {296--321},
     publisher = {mathdoc},
     volume = {33},
     year = {1959},
     zbl = {0111.29206},
     url = {http://geodesic.mathdoc.fr/item/CMH_1959__33_139177/}
}