Serasinghe, D. K. S.; Opatha, H.H.D.N.P.(Department of Human Resource Management Faculty of Management Studies and Commerce University of Sri Jayewardenepura, 2007)
Ali, M.A.M.H.; Opatha, H.H.D.N.P.(Department of Human Resource Management Faculty of Management Studies and Commerce University of Sri Jayewardenepura, 2008)