R. D. Daheriya, Suraj Shrivastava, and Manoj Ughade. “Parametric Metric Space, Parametric B-Metric Space and Expansive Type Mapping”. International Journal of Mathematics And Its Applications, vol. 4, no. 1 - C, Feb. 2016, pp. 107-1, http://ijmaa.in/index.php/ijmaa/article/view/603.