D. DeTruck, H. Gluck, D. Pomerleano, D.S. Vick. The four vertex theorem and its converse // Notices of the American Mathematical Society. — 2007. — Т. 54, вып. 2. — С. 9268. — Bibcode: 2006math......9268D. — arXiv:math/0609268.
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D. DeTruck, H. Gluck, D. Pomerleano, D.S. Vick. The four vertex theorem and its converse // Notices of the American Mathematical Society. — 2007. — Т. 54, вып. 2. — С. 9268. — Bibcode: 2006math......9268D. — arXiv:math/0609268.