R. N. Singh, S. K. Pandey, and Kiran Tiwari. “On Quarter-Symmetric Metric Connection in an Indefinite Sasakian Manifold”. Journal of International Academy of Physical Sciences, vol. 17, no. 3, Sept. 2013, pp. 255-7, https://www.iaps.org.in/journal/index.php/journaliaps/article/view/554.