W. P.  Maddison, ?Missing Data versus Missing Characters in Phylogenetic Analysis?, Systematic Biology, vol. 42, pp. 576-581, 1993.

E. A.  Kellogg, ?Phylogenetic structure in the grass family (Poaceae) as inferred from chloroplast DNA restriction site variation?, American Journal of Botany, vol. 80, pp. 1444-1454, 1993.

M. R.  Duvall, Peterson, P. M., Terrell, E., and Christensen, A. H., ?Phylogeny of North American oryzoid grasses as constructed from maps of plastid restriction sites?, American Journal of Botany, vol. 80, pp. 83-88, 1993.

J. I.  Davis and Soreng, R., ?Phylogenetic structure in the grass family (Poaceae) as inferred from chloroplast DNA restriction site variation?, American Journal of Botany, vol. 80, pp. 1444-1454, 1993.