Equipment, Organizations, etc
Here's a great article on why you should consider umpiring baseball games.
How to Become a Baseball Umpire
NFHS (National Federation of State High School Associations )
And Speaking for the NFHS, here's a link to their site's explanation of the new
P/DH rule: https://nfhs.org/sports-resource-content/baseball-rules-interpretations-2020/
You may have to log into the NFHS's site to view this.
NASO (The National Association of Sports Officials)
And this one was submitted by Jordan Sadler
https://wizardpins.com/blogs/blog/the-sport-of-baseball-useful-terms-to-know
https://blogs.fangraphs.com/maybe-theres-no-such-thing-as-a-perfectly-fair-strike-zone/