Simarjeet Kaur Bhatia, and Ram Shankar Gupta. “Symmetry Vector Fields on the 4-Dimensional Riemannian and Lorentzian Lie Group Sol^4_0”. International Journal of Maps in Mathematics, vol. 9, no. 2, Sept. 2026, pp. 200-18, https://simadp.com/journalmim/article/view/510.