Cirsium rhizocephalum subsp. sinuatum Cirsium rhizocephalum var. rhizocephalum Cirsium rhizocephalum var. sinuatum Cirsium esculentum subsp. frickii Cirsium grumosum Cirsium frickii Cirsium esculentum var. caucasicum Cirsium rhizocephalum subsp. rhizocephalum Cirsium rhizocephalum subsp. frickii Cirsium esculentum subsp. caucasicum
World Flora Online, http://www.worldfloraonline.org/, accessed June 20, 2024