:Sources are always the solution, if you want to start putting in footnotes and refs, that's a VERY good idea.  Ideally, a cite to the rule by number and with a URL to at least the rule book overview page is best.   However, for an international sport like this one, starting with the FEI, which oversees all international sport, is needed, even if there's other folks who are involved.  If other groups have significant influence, then their rules should also be cited and if there is some way to cite to a source, it helps to explain the unwritten rules (god knows every discipline has them, sometimes best to try and best to just avoid discussing fads altogether if they change frequently).  All that said, I'm also a little worried about this article drawing a "globalize" tag if it's too US-centric, so helpful to keep that in mind.