APA (7th ed.) Citation

Sheikheldin, S. Y., & unknown. (1991). Chemical Analysis of Some Penicillin And Cephalosporin Drugs.

Chicago Style (17th ed.) Citation

Sheikheldin, Sami Yassin, and unknown. Chemical Analysis of Some Penicillin And Cephalosporin Drugs. 1991.

MLA (9th ed.) Citation

Sheikheldin, Sami Yassin, and unknown. Chemical Analysis of Some Penicillin And Cephalosporin Drugs. 1991.

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