Sutaryanto. “AN EASY WAY OF ASKING QUESTIONS ”. Langit Biru: Jurnal Ilmiah Aviasi 2, no. 3 (June 30, 2009): 41-48. Accessed June 12, 2026. https://journal.ppicurug.ac.id/index.php/jurnal-ilmiah-aviasi/article/view/275.