Vukmirović, Srdjan, and Tijana Šukilović. 2020. “Geodesic Completeness of the Left-Invariant Metrics on ${{\mathbb{R}} H^n} $”. Ukrains’kyi Matematychnyi Zhurnal 72 (5), 611–619. https://doi.org/10.37863/umzh.v72i5.645.