APA (7th ed.) Citation

Liccardo, A., Pezzella, F., & Marotta, R. (1999). Consistent off-shell tree string amplitudes.

Chicago Style (17th ed.) Citation

Liccardo, A., F. Pezzella, and R. Marotta. Consistent Off-shell Tree String Amplitudes. 1999.

MLA (9th ed.) Citation

Liccardo, A., et al. Consistent Off-shell Tree String Amplitudes. 1999.