N.A. Assad and W. A. Kirk, Fixed point theorems for set-valued mappings of contractive type, Pacific J. Math. 43 (1972) 533-562.
 T. G. Bahaskar and V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. 65 (2006) 1379-1393.
 I. Beg and A. Rashid Butt, Fixed point of set-valued graph contractive mappings, J. Inequal. Appl. 2013 (2013) 252.
 I. Beg, A. Rashid Butt and S. Radojevic, The contraction principle for set-valued mappings on a metric space with a graph, Comput. Math. Appl. 60 (2010) 1214-1219.
 J. Gross and J. Yellen, Graph Theory and its Applications, CRC Press, 1998.
 J. Jamchymski, The contraction principle for mappings on a metric space with a graph, Proc. Amer. Math. Soc. 136 (2008) 1359-1373.
 S. B. Nadler, Multivalued contraction mappings, Pacific J. Math. 30 (1969) 475-487.
 M. Ozturk and E. Girgin, On some fixed-point theorems for ψ-contraction on metric space involving a graph, J. Inequal. Appl. 2014 (2014) 39.
 A. Petrusel and I. A. Rus, Fixed point theorems in ordered L-spaces, Proc. Amer. Math. Soc. 134 (2006) 411-418.