Uji kesahihan eksternal terhadap kuesioner gastroesophageal reflux disease quality of life berbahasa Indonesia untuk menilai kualitas hidup pasien gerd di poli ilmu penyakit dalam RSUK Tebet = External validity test of indonesian version of gastroesophageal reflux disease quality of life questionnaire to evaluate quality of life among gerd patients in internal medicine clinic at Tebet District Public Hospital