A Correlation study between students' motivation and vocabulary mastery toward writing ability at the eighth grade students of MTSN Gondangrejo in the academic year of 2014/2015 - Nurul Tri Kusuma Wati (Jurusan Pendidikan Bahasa Inggris Fakultas Ilmu Tarbiyah dan Keguruan IAIN Surakarta, 2015)