Guest editorial: IoT sensing, applications, and technologies for smart sustainable cities. Issue 3 (16th October 2021) - Hancke, Gerhard P.; Salehizadeh, Mohammad Reza; Liu, Xuan; Hu, Jie; Abu‐Mahfouz, Adnan M.; Thomos, Nikolaos; Ishihara, Susumu; Savaglio, Claudio