XINGLI, XU. 2013. “ANALYSIS OF THE SPEAKING MATERIALS IN TEXTBOOK‘MANDIRI:PRACTISE YOUR ENGLISH COMPETENCE (FOR SMK AND MAK XI)’BASED ON 2006 ENGLISH STANDARD OF CONTENT (SI)”. RETAIN : Journal of Research in English Language Teaching 1 (3). https://ejournal.unesa.ac.id/index.php/retain/article/view/3475.