<ref name="Helms_Cahan_et_al_2006">{{cite journal |first1=S. |last1=Helms Cahan |first2=G. E. |last2=Julian |first3=T. |last3=Schwander |first4=L. |last4=Keller |year=2006 |title=Reproductive isolation between ''Pogonomyrmex rugosus'' and two lineages with genetic caste determination |url=https://antcat.org/documents/4429/Helms Cahan et al 2006 Ecology.pdf |journal=Ecology |publisher= |volume=87 |issue= |pages=2160–2170 |doi= }}</ref>