There are several ways to do citation. I'm not talking about Chicago versus MLA but rather where you physically place the information. My favorite is as a footnote because I can just flick my eyes down to the bottom of the page without much effort. However sometimes these become cumbersome; it's not unusual in many academic articles for the page to consist solely of footnotes and there are only two lines of the actual article itself. For that reason many authors employ endnotes so that the reader isn't distracted from the narration. I personally hate this because I have to keep a finger where the endnotes are and constantly flip back to the end of the book. If you're reading something that's heavily annotated like The Divine Comedy or Ulysses, this is just a nightmare.

But the worst, the absolute fucking worst, is when the author doesn't even inform you that there's a citation. Usually you have a number or symbol superscripted at the of the sentence. I use it a lot. But I guess some authors feel the numbers ruin the aesthetic feel of the page or something and don't even put that in. They have endnotes and put a quotation there for you to know what it's referencing to. Let me give an example of a book I read recently. Here is how it should've been done:

Rutilius and Scaurus did so and were neither disbelieved nor criticized.^1
1 Publius Rutilius Rufus, born c. 160BC, consul 105 BC and a distinguished military commander, was an adhere of Stoic philosophy.

Instead what happened is there was no number at all after "criticized" and at the end of the book under the heading "notes to pages 3-4" it said:

Rutilius: Publius Rutilius Rufus, born c. 160 BC...

So first off I didn't even realize there was any note for Rutilius telling me who he was. It was only about ten pages in that I realized it was odd I hadn't hit a single notation yet, so I thumbed through the back to see if there were anyway. Once I realized what the idiot editor had done, the book no longer became enjoyable for me. Because it's now a fucking word search game. One of the endnotes was for the phrase "new peoples" somewhere on pages 23-25. Instead of reading the text and absorbing the knowledge, I'm spending all my time trying to find where the fuck "new peoples" are.

And seriously, this is a book by an ancient Roman author about the emperor Agricola.^* Who the fuck else besides people like me are going to read this thing? It's not this is meant for middle school students and you don't want to freak them out with an overload of information. This is clearly meant for people who are into history and want to read primary sources. Why are you trying to make these pages seem less cluttered? Just throw in the goddamned numbers already. We're used to it. We can handle it.

^* P. Cornelius Tacitus, Agricola, trans. by A. R. Birley (New York: Oxford University Press, 1999). SEE, THAT'S HOW YOU FUCKING DO IT.