RATNAWATI, D. “THE EFFECT OF USING CO-OP CO-OP TECHNIQUE IN TEACHING WRITING NARRATIVE TEXT TO THE TENTH GRADERS OF SMAN 3 SIDOARJO”. RETAIN : Journal of Research in English Language Teaching, Vol. 3, no. 2, July 2015, https://ejournal.unesa.ac.id/index.php/retain/article/view/12391.