Vukmirović, Srdjan, and Tijana Šukilović. “Geodesic Completeness of the Left-Invariant Metrics on ${{\mathbb{R}} H^n} $”.
Ukrains’kyi Matematychnyi Zhurnal 72, no. 5 (March 29, 2020): 611–619. Accessed April 7, 2025.
https://umj.imath.kiev.ua/index.php/umj/article/view/645.