1. G. Calugareanu, “L'integrale de Gauss et I'analyse des noeuds tridimensionnels” Rev. Math. Pures Appl.,4, No. 1, 5–20 (1959).
2. M. Barner, “Über die Mindestanzahl stationärer Schmiegebenen bei geschlossen streng-konvexen Raumkurven,” Abh. Math. Sem. Univ. Hamburg,20, 196–215 (1956).
3. V. I. Arnold, “On the number of flattening points on space curves,” Institute Mittag-Leffler. Report no.1, (1994–1995), pp. 1–13.
4. V. D. Sedykh, “A theorem on four vertices for a spatial curve,” Funkts. Anal. Prilozhen.26, No. 1, 35–41 (1992).
5. M. C. Romero-Fuster and V. D. Sedykh, “A lower estimate for the number of zero-torsion points of a space curve,” Beiträge Algebra Geom.,38, No. 1, 183–192 (1978).