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Mark W. Chase, Douglas E. Soltis, Richard G. Olmstead, David Morgan, Donald H. Les, Brent D. Mishler, Melvin R. Duvall, Robert A. Price, Harold G. Hills, Yin-Long Qiu, Kathleen A. Kron, Jeffrey H. Rettig, Elena Conti, Jeffrey D. Palmer, James R. Manhart, Kenneth J. Sytsma, Helen J. Michaels, W. John Kress, Kenneth G. Karol, W. Dennis Clark, Mikael Hedren, Brandon S. Gaut, Robert K. Jansen, Ki-Joong Kim, Charles F. Wimpee, James F. Smith, Glenn R. Furnier, Steven H. Strauss, Qui-Yun Xiang, Gregory M. Plunkett, Pamela S. Soltis, Susan M. Swensen, Stephen E. Williams, Paul A. Gadek, Christopher J. Quinn, Luis E. Eguiarte, Edward Golenberg, Gerald H. Learn, Jr., Sean W. Graham, Spencer C. H. Barrett, Selvadurai Dayanandan, Victor A. Albert, Phylogenetics of Seed Plants: An Analysis of Nucleotide Sequences from the Plastid Gene rbcL, Annals of the Missouri Botanical Garden, Vol. 80, No. 3 (1993), pp. 528-548+550-580
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Chase et al. (1993) studied this question.
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