APA (7th ed.) Citation

Halliday, G., Argent, G. C., & Hawksworth, D. L. (1967). Some Irish plant records.

Chicago Style (17th ed.) Citation

Halliday, G., G. C. Argent, and D. L. Hawksworth. Some Irish Plant Records. 1967.

MLA (9th ed.) Citation

Halliday, G., et al. Some Irish Plant Records. 1967.