Angiosperm Phylogeny Group. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society. 2016, 181 (1): 1–20. doi:10.1111/boj.12385.
Robert W. Scotland & Alexandra H. Wortley, How many species of seed plants are there?, Taxon, 2003, 52 (1): 101–104, JSTOR 3647306, doi:10.2307/3647306
Robert W. Scotland & Alexandra H. Wortley, How many species of seed plants are there?, Taxon, 2003, 52 (1): 101–104, JSTOR 3647306, doi:10.2307/3647306