https://www.acm.org/articles/bulletins/2020/march/dl-access-during-covid-19

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We believe that ACM can help support research, discovery and learning during this time of crisis by opening the ACM Digital Library to all. For the next three months, there will be no fees assessed for accessing or downloading work published by ACM. ... the ACM DL is now open, and will continue that way through June 30, 2020.

https://dl.acm.org/