KARPENKOV, Oleg. Elementary notions of lattice trigonometry. MATHEMATICA SCANDINAVICA, [S. l.], v. 102, n. 2, p. 161–205, 2008. DOI: 10.7146/math.scand.a-15058. Disponível em: https://tidsskrift.dk/math/article/view/15058. Acesso em: 13 aug. 2026.