Gauge theory on $Z_2 \times Z_2 \ti Z_2 $ Discrete Group and a   Spontaneous $CP$ Violation Toy Model
  In the spirit of Non-commutative differential calculus on discrete group, we construct a toy model of spontaneous $CP$ violation (SCPV). Our model is different from the well-known Weinberg-Branco model although it involves three Higgs doublets and preserve neutral flavor current conservation (NFC) after using the $Z_2 \ti Z_2 \ti Z_2$ discrete symmetry and imposing some constraints on Yukawa couplings. 
Bin Chen, Hao-Gang Ding and Ke Wu