Ngoc, Bui Hoang, and Le Mai Hai. “Time-Frequency Nexus Between Tourism Development, Economic Growth, Energy Consumption, and Ecological Footprint in Singapore”. Journal of Reviews on Global Economics 11 (August 28, 2022): 22–32. Accessed May 5, 2024. https://www.lifescienceglobal.com/pms/index.php/jrge/article/view/8787.