W. Greuter (2006). «Petasites hybridus». Compositae (pro parte majore). In: Euro+Med Plantbase - the information resource for Euro-Mediterranean plant diversity. Besøkt 11. februar 2020.
cropwildrelatives.org
P.A. Åsen (2009). «Plants of possible monastic origin, growing in the past or present, at medieval monastery grounds in Norway». I J.-P. Morel og A.M. Mercuri. Plants and Culture: seeds of the cultural heritage of Europe. Edipuglia. s. 227–238.
denvirtuellafloran.se
«Pestskråp». Den virtuella floran. Arkivert fra originalen 13. juli 2022. Besøkt 11. februar 2020.
doi.org
V. Kisielius m.fl. (2020). «The invasive butterbur contaminates stream and seepage water in groundwater wells with toxic pyrrolizidine alkaloids». Scientific Reports. 10 (19784). ISSN2045-2322. doi:10.1038/s41598-020-76586-1.
V. Kisielius m.fl. (2020). «The invasive butterbur contaminates stream and seepage water in groundwater wells with toxic pyrrolizidine alkaloids». Scientific Reports. 10 (19784). ISSN2045-2322. doi:10.1038/s41598-020-76586-1.