Photo taken on Sept. 26, 2019 shows the first day covers with the "Guangdong-Hong Kong-Macao Greater Bay Area" special stamp sheetlets at Hong Kong General Post Office in south China's Hong Kong. The "Guangdong-Hong Kong-Macao Greater Bay Area" special stamp sheetlets were issued on Thursday in post offices of Hong Kong, Guangzhou and Macao. (Xinhua/Luo Huanhuan)