Floral diversity and pollination. 4 in Plant Breeding Systems, 2nd edition, pp. Johnson, S. D., and K. E. Steiner. Generalization vs specialization in plant pollination systems. Hodges, S. A. 1997.
Floral nectar spurs and diversification.
THU Judd et al., Ch. 8, pp. Kellogg, E. A. 2001. Evolutionary history of the grasses. Raven, Evert, and Eichhorn, 1999. Photosynthesis, light, and life pp.