1. ELISTAIRhttps://elistair.com/orion-tethered-drone/
2. Tethered drones for persistent aerial surveillance applications;Prior,2015
3. Persistent surveillance with small Unmanned Aerial Vehicles (sUAV): A feasibility study;Al Nuaimi,2018
4. Heavy Duty Tethered Cleaning Drones That Safely Wash Windows of High Altitude Skyscrapershttps://laughingsquid.com/aerones-skyscraper-window-washing-drone/