<i><a href="//commons.wikimedia.org/wiki/Alnus_incana" title="Alnus incana">Alnus incana</a></i> subsp. <i>rugosa</i> (syn. <i>Alnus rugosa</i>)
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 1: 613.
<a rel="nofollow" class="external free" href="https://plants.usda.gov/java/profile?symbol=ALINR&amp;photoID=alru3_001_avd.tif">http://plants.usda.gov/java/profile?symbol=ALINR&amp;photoID=alru3_001_avd.tif</a>