The purpose of this thesis is to review some results about the elliptic equation where s > 1 is a constant, and K(×) is a bounded Holder continuous function. In chapter 2 we give the proofs of the existence theorems and nonexistence results. In chapter 3 we discuss elliptic system of the form in R ,where a, b > 0 , and p and q are nonnegative continuous functions. We give nonexistence criteria of positive entire solutions for (1.4) under the basic assumption ab > 1. To reinforce our nonexistence criteria, we give existence theorems of positive entire solutions for (1.4) under the basic assumption that ab > 1 and p and q have spherical symmetry. Keywords: