Global positive coexistence of a nonlinear elliptic biological interacting model. 
The purpose of this note is to give a necessary and sufficient condition for the coexistence of positive solutions to a rather general type of elliptic predator-prey system of the Dirichlet problem on the bounded domain omega when omega is a subset of Rn is large.  The result is that the partial differential equation system possesses positive coexistence if and only if the corresponding ordinary differential equation system has positive equilibrium, the positive constant states.  This result thus yields an algebraically computable criterion for the positive coexistence of predator and prey in many biological models.