Microbial and heavy metal contamination in herbal medicine: a prospective study in the central region of Saudi Arabia oleh Sarah F. Alharbi, Ameerah I. Althbah, Amal H. Mohammed, Mishaal A. Alrasheed, Mukhtar Ismail, Khaled S. Allemailem, Abdullah M Alnuqaydan, Ahmed Mohammed Baabdullah, Azzam Alkhalifah