Psychological contract breaches and employee voice behaviour: The moderating effects of changes in social relationships.
By: Ng, Thomas W. H.; Feldman, Daniel C.; Butts, Marcus M. European Journal of Work & Organizational Psychology. Aug2014, Vol. 23 Issue 4, p537-553.

From good friends to good soldiers: A psychological contract perspective.
By: Shih, Chih-Ting; Lin, Cheng-Chen. Asia Pacific Journal of Management. Mar2014, Vol. 31 Issue 1, p309-326.