Yahya, H. A. A. (1986). Development of A Programmed Instruction Text for Saudi Arabian Intermediate School Geography. University of Denver, Faculty of Social Sciences.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Yahya, Hasan Ayel Ahmed. Development of A Programmed Instruction Text for Saudi Arabian Intermediate School Geography. U S A: University of Denver, Faculty of Social Sciences, 1986.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Yahya, Hasan Ayel Ahmed. Development of A Programmed Instruction Text for Saudi Arabian Intermediate School Geography. University of Denver, Faculty of Social Sciences, 1986.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.