@article{MM2_1990__68_2_155523,
     author = {E. Heintze and J.-H. Eschenburg},
     title = {Comparison {Theory} for {Riccati} equations.},
     journal = {Manuscripta mathematica},
     pages = {209--214},
     publisher = {mathdoc},
     volume = {68},
     number = {2},
     year = {1990},
     zbl = {0714.53029},
     url = {http://geodesic.mathdoc.fr/item/MM2_1990__68_2_155523/}
}