BHATTA, C. R. Low-dimensional Nilpotent Lie Groups G₄. Nepal Journal of Science and Technology, [S. l.], v. 10, p. 155–159, 2010. DOI: 10.3126/njst.v10i0.2951. Disponível em: https://nepjol.info/index.php/NJST/article/view/2951. Acesso em: 3 jul. 2024.