<i><b><a href="//commons.wikimedia.org/wiki/Plectocephalus_americanus" title="Plectocephalus americanus">Plectocephalus americanus</a></b></i> - como <i>Centaurea americana</i>
Thomas Meehan (drawn by Alois Lunzer)
1880
<i>The Native Flowers and Ferns of the United States</i>, vol 2, nº2, pl. 17, p. 69 <a rel="nofollow" class="external autonumber" href="https://www.biodiversitylibrary.org/page/18553074">[1]</a>