BioStor
 | Genus-group names of bees and supplemental family-group names Charles D Michener (1997) Scientific Papers Natural History Museum University of Kansas 1: 1-81 |
 | The biology of Hoplitis (Robertsonella) simplex (Cresson), with a synopsis of the subgenus Robertsonella Titus John L Nuff (2009) Journal of Hymenoptera Research 18(2): 151-166 |