REFERENCE

  1. Prof. Dr. Babikir Idrees Babikir. University of Khartoum. HP: 0912134593.
  2. Prof. Dr. Mohamed Khair Abd elrahman, Vice chancelor of University of Sinnar. HP: 0912333245.
  3. Prof. Dr. Abdalla Mohamed Abdalla. University of Kordofan. HP: 0912999087.