1. British Broadcasting Company (2020), ‘US oil price turns negative as demand dries up’, BBC News, 20 April, https://www.bbc.com/news/business-52350082. Accessed 8 September 2021.
2. Chan, Chun Sing (2020), ‘Singapore can still make a living in a more protectionist world: Chan Chun Sing’, YouTube, 14 June, https://www.youtube.com/watch?v=g2OGl0AQrm0. Accessed 30 September 2021.