Umpire Substance Checks Put Pitchers in Awkward Positions - The New York Times
Best Pine Tar & Baseball Rosin
Should Pine Tar Be Legal for Pitchers?, News, Scores, Highlights, Stats, and Rumors
Why do MLB players have pine tar on their helmets? - Quora
A gripping saga: 11 tales of pitchers using spitters, sandpaper and scuffing - Sports Illustrated
Here is how the Red Sox will handle the three-batter rule for pitchers - The Boston Globe
Should Pine Tar Be Legal For Pitchers?, by The Caught Looking Show, Caught Looking
Joel Piñeiro: Five sleeper pitchers for fantasy baseball, mayonnaise's effect on spin rates, an Ichiro story and more - The Athletic
North Shore Tavern Mound Visit: How to use analytics to evaluate pitchers five different ways
Should we care if pitchers use pine tar?, Bronx Pinstripes
Opinion Five myths about major league pitching - The Washington Post
Should Pine Tar Be Legal For Pitchers?, by The Caught Looking Show, Caught Looking
Pine Tar in Baseball: What It Does, Using It & Rules
MLB pitchers using pine tar is against the rules, but everyone's OK with it
Why Pitchers Use Pine Tar