The IUCN RedList of Threatened Species v. 2016.1
Discover Life
Atlas Hymenoptera
Atlas of the European Bees: genus Andrena 1st Edition
Checklist of the Western Palaearctic Bees (Hymenoptera: Apoidea: Anthophila)
Wild Bees of Slovenia
BWARS - Bees, Wasps & Ants Recording Society