MLB Letter Confirms Yankees Used Technology for Sign Stealing - The New York Times

Yankees Letter Reveals Past Fine for Sign-Stealing Methods, per Report - Sports Illustrated

MLB letter to New York Yankees detailed illicit use of technology prior to 2017 sign-stealing edict - ABC13 Houston

THEY CHEATED TOO: 'Yankee Letter' revealed, documents sign-stealing techniques and punishment from MLB

MLB Letter Confirms Yankees Used Technology for Sign Stealing - The New York Times

MLB letter to New York Yankees detailed illicit use of technology prior to 2017 sign-stealing edict - ESPN

Disclaimer: I'm not an Astros fan. : r/mlb

Details emerge about Carlos Beltrán's role in the 2017 Astros clubhouse and the team's sign-stealing scheme - The Athletic

Sign of times: Major League Baseball gives OK to electronic pitch calling