Magallon, S.; Sanderson, M. J. (1 de dezembro de 2002). «Relationships among seed plants inferred from highly conserved genes: sorting conflicting phylogenetic signals among ancient lineages». American Journal of Botany (em inglês). 89 (12): 1991–2006. ISSN1537-2197. PMID21665628. doi:10.3732/ajb.89.12.1991
Friedman, William E. (1990). «Sexual Reproduction in Ephedra nevadensis (Ephedraceae): Further Evidence of Double Fertilization in a Nonflowering Seed Plant». American Journal of Botany. 77 (12): 1582–1598. JSTOR2444491. doi:10.1002/j.1537-2197.1990.tb11399.x
Carmichael, Jeffrey S.; Friedman, William E. (1996). «Double Fertilization in Gnetum gnemon (Gnetaceae): Its Bearing on the Evolution of Sexual Reproduction within the Gnetales and the Anthophyte Clade». American Journal of Botany. 83 (6): 767–780. JSTOR2445854. doi:10.1002/j.1537-2197.1996.tb12766.x
Friedman, William E. (1994). «The Evolution of Embryogeny in Seed Plants and the Developmental Origin and Early History of Endosperm». American Journal of Botany. 81 (11): 1468–1486. JSTOR2445320. doi:10.1002/j.1537-2197.1994.tb15633.x
Zenkteler, M. (1990). «In vitro fertilization and wide hybridization in higher plants». Crit Rev Plant Sci. 9 (3): 267–279. doi:10.1080/07352689009382290
Friedman, William E. (1990). «Sexual Reproduction in Ephedra nevadensis (Ephedraceae): Further Evidence of Double Fertilization in a Nonflowering Seed Plant». American Journal of Botany. 77 (12): 1582–1598. JSTOR2444491. doi:10.1002/j.1537-2197.1990.tb11399.x
Carmichael, Jeffrey S.; Friedman, William E. (1996). «Double Fertilization in Gnetum gnemon (Gnetaceae): Its Bearing on the Evolution of Sexual Reproduction within the Gnetales and the Anthophyte Clade». American Journal of Botany. 83 (6): 767–780. JSTOR2445854. doi:10.1002/j.1537-2197.1996.tb12766.x
Friedman, William E. (1994). «The Evolution of Embryogeny in Seed Plants and the Developmental Origin and Early History of Endosperm». American Journal of Botany. 81 (11): 1468–1486. JSTOR2445320. doi:10.1002/j.1537-2197.1994.tb15633.x
Magallon, S.; Sanderson, M. J. (1 de dezembro de 2002). «Relationships among seed plants inferred from highly conserved genes: sorting conflicting phylogenetic signals among ancient lineages». American Journal of Botany (em inglês). 89 (12): 1991–2006. ISSN1537-2197. PMID21665628. doi:10.3732/ajb.89.12.1991
Magallon, S.; Sanderson, M. J. (1 de dezembro de 2002). «Relationships among seed plants inferred from highly conserved genes: sorting conflicting phylogenetic signals among ancient lineages». American Journal of Botany (em inglês). 89 (12): 1991–2006. ISSN1537-2197. PMID21665628. doi:10.3732/ajb.89.12.1991