Reference
Antonio Barioni Gusman, Gerhard Gottsberger (1996): Differences in Floral Morphology, Floral Nectar Constituents, Carotenoids, and Flavonoids in Petals of Orange and Yellow Pyrostegia venusta (Bignoniaceae) Flowers. – Phyton, Annales Rei Botanicae, Horn – 36_2: 161 - 171.