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2. Using drones to deliver critical humanitarian aid, WFP Drones, https://drones.wfp.org/updates/using-drones-deliver-critical-humanitarian-aid.
3. Uber elevate summit lays out 2023 flight plan;Siebenmark,2019
4. China lands chang’e-5 spacecraft on moon to gather lunar rocks and soil;Myers;N.Y. Times,2020
5. NASA says first Artemis Moon landing now expected in 2025;Harwood,2021