A scientific line drawing of Allium cernuum from Britton &amp; Brown 1913
Britton, N.L., and A. Brown. Scanned by Omnitek. Edited by User:Earthdirt.
1913
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 1: 498.