Compositae Working Group (CWG) (2025). Global Compositae Database.
Hieracium laevigatum subsp. rigidum (Hartm.) Čelak.. Accessed through: Marine Species Traits editorial board (2025) Marine Species Traits at: https://www.marinespecies.org/traits/aphia.php?p=taxdetails&id=1150764 on 2025-04-03
Marine Species Traits editorial board (2025). Marine Species Traits.
Hieracium laevigatum subsp. rigidum (Hartm.) Čelak.. Accessed at: https://www.marinespecies.org/traits/aphia.php?p=taxdetails&id=1150764 on 2025-04-03