Pollaro, Paul; Robertson, Paul (2022). “Reassessing the Role of Anthropogenic Climate Change in the Extinction of Silphium”. 《Frontiers in Conservation Science》 2. doi:10.3389/fcosc.2021.785962. ISSN2673-611X.
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Riddle, John M.; Estes, J. Worth (1992). “Oral Contraceptives in Ancient and Medieval Times”. 《American Scientist》 80 (3): 226–233. Bibcode:1992AmSci..80..226R. JSTOR29774642.
Pollaro, Paul; Robertson, Paul (2022). “Reassessing the Role of Anthropogenic Climate Change in the Extinction of Silphium”. 《Frontiers in Conservation Science》 2. doi:10.3389/fcosc.2021.785962. ISSN2673-611X.