Masal’tsevL. A. (2005) “On Isometric Immersion of Three-Dimensional Geometries $SL_2$, $Nil$ and $Sol$ into a Four-Dimensional Space of Constant Curvature”, Ukrains’kyi Matematychnyi Zhurnal, 57(3), pp. 421–426. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3609 (Accessed: 22November2024).