Seifert, Bernhard. “Formica Nigricans Emery, 1909 - an Ecomorph of Formica Pratensis Retzius, 1783 (Hymenoptera, Formicidae)”. Entomologica Fennica, vol. 2, no. 4, Dec. 1991, pp. 217-26, https://doi.org/10.33338/ef.83554.