Sofiati, A. “THE EFFECT OF EXTERNAL FACTORS’ OF SELF-EFFICACY TOWARDS STUDENTS’ PERFORMANCE IN PUBLIC SPEAKING EXTRACURRICULAR IN SENIOR HIGH SCHOOL”. RETAIN : Journal of Research in English Language Teaching, Vol. 8, no. 1, Feb. 2020, https://ejournal.unesa.ac.id/index.php/retain/article/view/32205.