Reference:
Queller, David & Zacchi, Francesca & Cervo, Rita & Turillazzi, Stefano & Henshaw, Michael & Santorelli, Lorenzo & Strassmann, Joan. (2000). Unrelated helpers in a social insect. Nature. 405. 784-7. 10.1038/35015552.
URL:
https://www.researchgate.net/publication/12453010_Unrelated_helpers_in_a_social_insect