GRAFAREND, E. W. Field lines of gravity, their curvature and torsion, the Lagrange and the Hamilton equations of the plumbline. Annals of Geophysics, [S. l.], v. 40, n. 5, 1997. DOI: 10.4401/ag-3859. Disponível em: https://www.annalsofgeophysics.eu/index.php/annals/article/view/3859. Acesso em: 4 aug. 2021.