A closed-form necessary and sufficient condition for any two-qubit state   to show hidden nonlocality w.r.t the Bell-CHSH inequality
  In this note, we discuss a closed-form necessary and sufficient condition for any two-qubit state to show hidden nonlocality w.r.t the Bell-CHSH inequality. This is then used to numerically compute the relative volume of states showing hidden Bell-CHSH non-locality , among all two-qubit states with one-sided reduction maximally mixed. 
Rajarshi Pal, Sibasish Ghosh
quant-ph