1. Tropical woody Rubiaceae;E Robbrecht;Opera Bot Belgica,1988
2. Govaerts R, Ruhsam M, Andersson L, Robbrecht E, Bridson D, Davis A, et al. World checklist of Rubiaceae; 2017 [cited 4 December 2017]. Facilitated by the Royal Botanic Gardens, Kew. Available from: http://wcsp.science.kew.org/
3. Catchweed bedstraw or cleavers, Galium aparine L.—a very “sticky” subject;MS Defelice;Weed Technol,2002
4. cpDNA intergene sequences corroborate restriction site data for reconstructing Rubiaceae phylogeny;F Ehrendorfer;Plant Syst Evol,1994
5. Phylogeny of Rubiaceae-Rubieae inferred from the sequence of a cpDNA intergene region;JF Manen;Plant Syst Evol,1994