1. Size and shape in ontogeny and phylogeny;Alberch;Paleobiology,1979
2. Lower Cretaceous floras of western Canada;Bell;Mem.-Geol. Surv. Can.,1956
3. Gymnosperms—Structure and Evolution;Chamberlain,1934
4. The Jehol Biota,2003
5. Morphology of Gymnosperms;Coulter,1917