1. Production of vitamin B12 by propionic acid bacteria. II. Effect of nutritional and environmental factors on vitamin B12 production by Propionibacterium shermanii;Abdel-Hafez;Ann. Agric. Sci.,1983
2. AMPCO, 1998. Report of the Agricultural Marketing and Processing Company of Jordan. Al-Mafraq Publishing House Amman, Jordan
3. AOAC, 1995. Official Methods of Analysis, 16th ed. Association of Official Analytical Chemists, Washington
4. ATCC, 1994. American Type Culture Collection, Instructions for Rehydration of Freeze-Dried Cultures. Kockville, Maryland, USA
5. Biotechnology: A Textbook of Industrial Microbiology;Brock,1984