Navaruttanaporn, Srijittra. “A Study on the Effects of Self-Learning Media Packages on the Retention of English-Speaking Skills: A Case Study of Front Desk Staff at Loei Palace Hotel, Loei Province”. Research and Development Journal, Loei Rajabhat University 21, no. 77 (August 18, 2026): 105–119. accessed September 14, 2026. https://so05.tci-thaijo.org/index.php/researchjournal-lru/article/view/281967.