@article{PORMA_1979__38_1-2_115372,
     author = {Cheng, Sui-Sun},
     title = {Sturmian theorems for components of coupled elliptic systems},
     journal = {Portugaliae mathematica},
     pages = {113--117},
     publisher = {mathdoc},
     volume = {38},
     number = {1-2},
     year = {1979},
     mrnumber = {0682359},
     zbl = {0517.35006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1979__38_1-2_115372/}
}