What is the earliest documented usage of the term "Sola Scriptura"? While the concept may have existed far prior, a recent discussion has left me wondering - What is the earliest documented usage of the term "Sola Scriptura" in Christian writings. I am not interested in articulation of the concept, but instead of the first documented usage of this specific and actual phrase in reference to the doctrine (not just coincidental usage) - so please be sure to include a quote in your answer.
In 1520 Luther wrote the following in his defense against the bull of Pope Leo X:


  Nolo omnium doctior iactari, sed solam scripturam regnare, nec eam meo spiritu aut ullorum hominum interpretari, sed per seipsam et suo spiritu intelligi volo. (WA 7:98.40–99.2)


Mark D. Thompson gives this translation:


  I do not want to throw out all those more learned [than I], but Scripture alone to reign, and not to interpret it by my own spirit or the spirit of any man, but I want to understand it by itself and its spirit.