Polemonium occidentale subsp. amygdalinum Polemonium caeruleum subsp. amygdalinum Polemonium occidentale var. intermedium Polemonium intermedium Polemonium helleri Polemonium caeruleum var. foliosissimum Polemonium caeruleum var. pterosperma
World Flora Online, http://www.worldfloraonline.org/, accessed June 20, 2024