Gufron. (2008). The attitude of UIN (Universitas Islam Negeri) Jakarta students towards group discussion in learning English: A case study. Kulliyyah of Islamic Revealed Knowledge and Human Sciences, International Islamic University Malaysia.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Gufron. The Attitude of UIN (Universitas Islam Negeri) Jakarta Students Towards Group Discussion in Learning English: A Case Study. Gombak, Selangor: Kulliyyah of Islamic Revealed Knowledge and Human Sciences, International Islamic University Malaysia, 2008.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Gufron. The Attitude of UIN (Universitas Islam Negeri) Jakarta Students Towards Group Discussion in Learning English: A Case Study. Kulliyyah of Islamic Revealed Knowledge and Human Sciences, International Islamic University Malaysia, 2008.