R_F Parity and Almost Massless Up Quark
  We introduce a parity $R_F$ to introduce naturally small masses for the first family members and in particular almost massless $u$ quark toward the strong CP solution. We also discuss the phenomenological implications of this model on the proton decay and the neutrino mass. Furthermore, it is possible to embed this $R_F$ parity to local $U(1)_R$ gauge symmetry. 
Jihn E. Kim, Bumseok Kyae, and Jae Sik Lee