Antimicrobial Effects of Thymoquinone on Entamoeba histolytica and Giardia lamblia, Sheikh, Bassem Yousef, Taha Manal Mohamed El, Koko Waleed Syaed, and Abdelwahab Siddig Ibrahim , Pharmacognosy Journal, December 2015, Volume 8, Issue 2, p.168-170, (2015)