damascusuniversity.sy/mag/human/images/stories/289-331.pdf
libback.uqu.edu.sa/hipres/ABS/ind10596.pdf
uqu.edu.sa/files2/tiny_mce/plugins/filemanager/files/.../4042%20.pdf
libback.uqu.edu.sa/hipres/ABS/ind10596.pdf
uqu.edu.sa/files2/tiny_mce/plugins/filemanager/files/.../4042%20.pdf