Khalaf, A. S. S. (1989). The Effects of Classroom Testing Frequency on Student Achievement in Tenth Grade Biology in Saudi Arabia. Kansas State University, College of Education.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Khalaf, Abdulkhalig S. S. The Effects of Classroom Testing Frequency on Student Achievement in Tenth Grade Biology in Saudi Arabia. Manhhattan, Kansas: Kansas State University, College of Education, 1989.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Khalaf, Abdulkhalig S. S. The Effects of Classroom Testing Frequency on Student Achievement in Tenth Grade Biology in Saudi Arabia. Kansas State University, College of Education, 1989.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.