Vladimir Varićak
[1][2] Varićak, an ethnic Serb, was born on March 1, 1865, in the village of Švica near Otočac, Austrian Empire (present-day Croatia).He continued to develop the hyperbolic reinterpretation of Einstein's theory collecting his results in 1924 in a textbook, Darstellung der Relativitätstheorie im drei-dimensionalen Lobatschefskijschen Raume (Relativity in Three-Dimensional Lobachevski Space), now available in English.He begins by analysis of "the tip of a four-dimensional velocity vector" and notes Minkowski's equations where "both hypersurfaces provide a basis for a well-known model of non-Euclidean space of constant negative curvature, popularized by Helmholtz."[9] Walter goes on to say: Varićak is also known as a high school teacher of Milutin Milanković and of Mileva Marić, the first wife of Einstein,[10] and as a university instructor of Đuro Kurepa.Varićak made scholarly contributions on the life and work of Ruđer Bošković (1711–1787) These are listed in the biography of Kurepa (1965) cited below.