Huneke-Wiegand Conjecture for Complete Intersection Numerical Semigroup   Rings
  We give a positive answer to the Huneke-Wiegand Conjecture for monomial ideals over free numerical semigroup rings, and for two generated monomial ideals over complete intersection numerical semigroup rings. 
Pedro A. Garcia-Sanchez, Micah J. Leamer
math.AC math.NT