Rad, Soleimani G., and H. Rahimi. 2013. “Common Fixed-Point Theorems and <em class="a-Plus-plus">c</Em&gt;-Distance in Ordered Cone Metric Spaces”. Ukrains’kyi Matematychnyi Zhurnal 65 (12), 1667–1680. https://umj.imath.kiev.ua/index.php/umj/article/view/2545.