@article{EJDE_2011__2011__a99,
     author = {Tyagi, Jagmohan},
     title = {Existence of non-negative solutions for predator-prey elliptic systems with a sign-changing nonlinearity},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2011},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2011__2011__a99/}
}