Ismat Beg and  Asma Rashid Butt,  Fixed Point Theorems for Set Valued Mappings in Partially Ordered Metric Spaces.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    September 2013, vol. 74(2). 249 - 251
    [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/16981.