from D.H. Kent 1990; Flora Europaea ed.2 vol.1 appendix 1 from R.E.G.Pichi Sermolli 1 March 1991; Death year in: Schlechtendalia 36: Abb. 2-3. 2019, http://webcache.googleusercontent.com/search?q=cache:hRzPy8QQ5gkJ:www.arktisch-alpiner-garten.de/Bilder/JESSEN_2019-2.pdf&cd=12&hl=de&ct=clnk&gl=ch&client=firefox-b-d (via Boris Heuer)