F. Verloove, E. Sanchez Gullon, and A. Guiggi, “On ’Opuntia spinulifera’ and ’O. streptacantha’ (Cactaceae), new to Spain, and the status of ’O. huajuapensis’ in that country”, Mediterr. Bot., vol. 41, no. 1, pp. 121–125, Feb. 2020, doi: https://doi.org/10.5209/mbot.62978