Key points are not available for this paper at this time.
Jeff J. Doyle, Jane L. Doyle, A. H. D. Brown, Chloroplast DNA Phylogenetic Affinities of Newly Described Species in Glycine (Leguminosae: Phaseoleae), Systematic Botany, Vol. 15, No. 3 (Jul. - Sep., 1990), pp. 466-471
Doyle et al. (Sun,) studied this question.