TY - JOUR AU - Tyagi, Jagmohan TI - Existence of non-negative solutions for predator-prey elliptic systems with a sign-changing nonlinearity JO - Electronic Journal of Differential Equations PY - 2011 VL - 2011 PB - mathdoc UR - http://geodesic.mathdoc.fr/item/EJDE_2011__2011__a99/ LA - en ID - EJDE_2011__2011__a99 ER -