W.L.Wagner & Lorence (Fosberg) 2005 - Terrell EE, Robinson HE, Wagner WL, Lorence DH (2005) Resurrection of Genus Kadua for Hawaiian Hedyotidinae (Rubiaceae), with Emphasis on Seed and Fruit Characters and Notes on South Pacific Species. Systematic Botany 30: 818-833. doi: 10.1600/036364405775097716.