You guy's are
killing me.
Inline references in ebooks (other than short parentheticals like this one) drive me absolutely batsh!t crazy.
It seems to me that shoe-horning notes and references inline is more of an attempt to "copy printed layout" (think footnotes) than links and endnotes would be. If it's too important for the reader to miss out on, then it shouldn't be a reference or note at all. It should already be a part of the main text. If it's anything other than a short parenthetical... link it and get it the hell out of the flow, I say (and include a return link for devices/apps that lack a "back" feature). At least until we get pop(up|over) balloon notes.