The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
TechCrunch (23 February 2019): the letter was sent to Nadella and Smith "the organizing group said Friday", i.e. 22 February; NPR's[6] story is dated 2019/02/22.
More than 50 employees signed a petition in February 2019; Nadella defended the contract.[1]
Background on the HoloLens headset line.[1]
History of the Integrated Visual Augmentation System program.[1]
Published 26 February 2019: over 250 employees, quotes from the letter and Nadella.[1]
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