1. Alcántara Rojas, B. 2008. Nepapan Xochitl: The power of flowers in the works of Sahagún. In Colors between two worlds: The Florentine codex of Bernardino de Sahagún, ed. L.A. Waldman, 106–132. Florence: Villa I Tatti.
2. Al-Shehbaz, I.A. 2012. Brassicaceae. In The Jepson manual. Vascular plants of California, ed. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Bosatti, and D.H. Wilken, 2nd ed., 512–577. Berkeley: University California Press.
3. Barlow, M. 1986. The Voynich manuscript—By Voynich? Cryptologia 10: 210–216.
4. Bayer, R.J., A.L. Bogle, and D.M. Cherniawsky. 2006. Petasites. In Flora of North America North of Mexico, ed. Flora of North America Editorial Committee, 635–637. Vol. 20. Magnoliophyta: Asteridae, Part 7: Asteraceae, Part 2. New York: Oxford University Press.
5. Berg, C.C. 2001. Moreae, Artocarpeae, and Dorstenia (Moraceae). Flora Neotropica 83: 1–346.