APA (7th ed.) Citation

Valko, L., Zikmund, M., & Tvaroška, I. Seventieth Birthday of Academician Vojtech Kellö.

Chicago Style (17th ed.) Citation

Valko, Ladislav, Miroslav Zikmund, and Igor Tvaroška. Seventieth Birthday of Academician Vojtech Kellö.

MLA (9th ed.) Citation

Valko, Ladislav, et al. Seventieth Birthday of Academician Vojtech Kellö.

Warning: These citations may not always be 100% accurate.