APA (7th ed.) Citation

Millard, A. R., Gaballa, G. A., & Ruffle, J. (1979). The Scythian Problem.

Chicago Style (17th ed.) Citation

Millard, A. R., G. A. Gaballa, and J. Ruffle. The Scythian Problem. Warminster, 1979.

MLA (8th ed.) Citation

Millard, A. R., et al. The Scythian Problem. 1979.