Khalaf, A. S. S., & Hanna, G. S. (1989). The Effects of classroom testing frequency on student achievement in tenth grade biology in Saudi Arabia. University of Pittsburgh.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Khalaf, Abdulkhalig S. S., و Gerald S. Hanna. The Effects of Classroom Testing Frequency on Student Achievement in Tenth Grade Biology in Saudi Arabia. Pittsburgh: University of Pittsburgh, 1989.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Khalaf, Abdulkhalig S. S., و Gerald S. Hanna. The Effects of Classroom Testing Frequency on Student Achievement in Tenth Grade Biology in Saudi Arabia. University of Pittsburgh, 1989.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.