“…In this model the populations of predator and prey permanently oscillate for almost all positive initial conditions. Recently, there have been some excellent works on global dynamics of resource competitive models (see [4,5,11,16,17,19,24,22,25,30,31,32,33,34]), which are important in understanding of the mechanism of natural selection: the principle of competitive exclusion (see [1,3,10,26,27,28,35,36]) or the coexistence of competing species. For example, Volterra [29] observed that the coexistence of two or more predators competing for fewer prey resources is impossible.…”