Four positive solutions of semilinear elliptic equations in exterior domains

In this paper, assuming that hh is nonnegative and ‖h‖L2>0‖h‖L2>0, we prove that if ‖h‖L2‖h‖L2 is sufficiently small, then there are at least four positive solutions of the semilinear elliptic equation in RN∖D¯, where DD is a C1,1C1,1 bounded domain in RNRN.