How do I cite Martin Luther in the Chicago style?

In all my sources, he is quoted with footnotes referring to LW or W and then numbers... I have no idea what this means. How do I quote Martin Luther, either letters or bodies of work (the actual books by him are easier to cite, but the letters and such I have no clue)? (I mean Martin Luther of the Reformation, not Martin Luther King Jr. by the way! ;)) I'm using the Chicago/Turabian style, although really if I have to switch styles to be able to do this I'm fine with that. Very confusing! Any help would be so appreciated.