MST has filled in the rule book issues, but on here you may see some other names mentioned.
Those are usually authors of official interpretations of baseball rules.... Umpiring can not be done at higher levels with just the rule book alone....there are these suplemental books and also books on mechanics to help shape your game.......
Hopkins: B. Elliott Hopkins (NFHS rules Interpreter)
Evans: Jim Evans Former MLB umpire, current owner of the Academy of Professional Umpiring (MLB school)
Jaksa/Roder: An Umpire manual with rules interps written by Chris Jaksa and Rick Roder...
there are others, but those are the best known....