APA (7th ed.) Citation

Al-Hajji, A. A., & unknown. (1990). Nickel and vanadyl porphyrins in Arabian heavy crude oil.

Chicago Style (17th ed.) Citation

Al-Hajji, Adnan Ahmed, and unknown. Nickel and Vanadyl Porphyrins in Arabian Heavy Crude Oil. 1990.

MLA (9th ed.) Citation

Al-Hajji, Adnan Ahmed, and unknown. Nickel and Vanadyl Porphyrins in Arabian Heavy Crude Oil. 1990.

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