^ abcTerrell, Edward E.; Robinson, Harold E.; Wagner, Warren L.; Lorence, David H. (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 (4): 818. doi:10.1600/036364405775097716. S2CID85617802.
^Adelbert von Chamisso and Diederich von Schlechtendal. 1829. Linnaea4:157. (see External links below)
^Warren L. Wagner, Derral R. Herbst, and Sy H. Sohmer. Manual of the Flowering Plants of Hawaii, Revised Edition, 1999. Bishop Museum Press: Hololulu, HI, USA.
^David H. Lorence, Warren L. Wagner, and William G. Laidlaw. 2010. "Kadua haupuensis (Rubiaceae: Spermacoceae), a new endemic species from Kauaʻi, Hawaiian Islands". Brittonia62(2):137-144. doi:10.1007/s12228-009-9103-y
^ abKarehed, J; Groeninckx, I; Dessein, S; Motley, T; Bremer, B (2008). "The phylogenetic utility of chloroplast and nuclear DNA markers and the phylogeny of the Rubiaceae tribe Spermacoceae". Molecular Phylogenetics and Evolution. 49 (3): 843–66. Bibcode:2008MolPE..49..843K. doi:10.1016/j.ympev.2008.09.025. PMID18950720.