Não informado. (1979). Focus on Learning Problems in Mathematics. Center for Teaching Learning on Mathematics.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Não informado. Focus on Learning Problems in Mathematics. Framingham, Mass: Center for Teaching Learning on Mathematics, 1979.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Não informado. Focus on Learning Problems in Mathematics. Center for Teaching Learning on Mathematics, 1979.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.