Key points are not available for this paper at this time.
James A. Doyle, Michael J. Donoghue, Elizabeth A. Zimmer, Integration of Morphological and Ribosomal RNA Data on the Origin of Angiosperms, Annals of the Missouri Botanical Garden, Vol. 81, No. 3 (1994), pp. 419-450
Doyle et al. (Sat,) studied this question.