Anthocyanin-flavone copigmentation in bluish purple flowers of Japanese garden iris (Iris ensata Thunb.) T. Yabuya, M. Nakamura, T. Iwashina, M. Yamaguchi and T. Takehara, EUPHYTICA, Volume 98, Number 3, 163–167, doi:10.1023/A:1003152813333
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"Iris ensata". Plant Heritage: National Council for the Conservation of Plants and Gardens. Retrieved 14 March 2018.