Links for Carduus spp., thistle
Databases
Search for Carduus spp. in the Global Biodiversity Information Facility (GBIF).
Search for Carduus spp. in the Encyclopedia of Life (EOL).
Search for known associations between Carduus spp. and plants in the Plant-SyNZ database.
Search for Carduus spp. in the Species 2000 & ITIS Catalogue of Life.
Taxonomy
Check the taxonomy of Carduus spp. in the Universal Biological Indexer and Organizer (uBio).
Scientific literature
Search the internet for scholarly articles about Carduus spp. using Google Scholar.
Images
Search for images of Carduus spp. on the internet using Google Images.