Improving students'vocabulary mastery by using picture story ( A Classroom action research for eighth grade students of SMP N 1 Sawit in the academic year of 2014/2015 - Nilawati Dyah Puspitarini (Jurusan Pendidikan Bahasa Inggris Fakultas Ilmu Tarbiyah dan Keguruan IAIN Surakarta, 2016)