Segre, Beniamino (1968), “Alcune proprietà differenziali in grande delle curve chiuse sghembe”, 《Rendiconti di Matematica》 1: 237–297, MR0243466
Weiner, Joel L. (1977), “Global properties of spherical curves”, 《Journal of Differential Geometry》 12 (3): 425–434, MR0514446. For the tennis ball theorem (applicable more generally to curves that are not contained in a single hemisphere), see Theorem 2, p. 427
Thorbergsson, Gudlaugur; Umehara, Masaaki (1999), 〈A unified approach to the four vertex theorems II〉, Tabachnikov, Serge, 《Differential and Symplectic Topology of Knots and Curves》, Amer. Math. Soc. Transl. Ser. 2 190, Amer. Math. Soc., Providence, RI, 229–252쪽, doi:10.1090/trans2/190/12, MR1738398. See in particular pp. 242–243.
Thorbergsson, Gudlaugur; Umehara, Masaaki (1999), 〈A unified approach to the four vertex theorems II〉, Tabachnikov, Serge, 《Differential and Symplectic Topology of Knots and Curves》, Amer. Math. Soc. Transl. Ser. 2 190, Amer. Math. Soc., Providence, RI, 229–252쪽, doi:10.1090/trans2/190/12, MR1738398. See in particular pp. 242–243.
Thorbergsson, Gudlaugur; Umehara, Masaaki (1999), 〈A unified approach to the four vertex theorems II〉, Tabachnikov, Serge, 《Differential and Symplectic Topology of Knots and Curves》, Amer. Math. Soc. Transl. Ser. 2 190, Amer. Math. Soc., Providence, RI, 229–252쪽, doi:10.1090/trans2/190/12, MR1738398. See in particular pp. 242–243.
projecteuclid.org
Weiner, Joel L. (1977), “Global properties of spherical curves”, 《Journal of Differential Geometry》 12 (3): 425–434, MR0514446. For the tennis ball theorem (applicable more generally to curves that are not contained in a single hemisphere), see Theorem 2, p. 427