Subsequently, the species were divided on the basis of their perenniality.
Michaela Kolářová, Luděk Tyšer, Josef Soukup 2015, 'Weed Species Diversity in the Czech Republic Under Different Farming and Site Conditions',Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensishttps://acta.mendelu.cz/63/3/0741/. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)