In Roger Warren's very interesting introduction to his Oxford edition of Henry VI, Part Two (2003), he delineates the surprising complexity involved in working with a play that has only two early versions. In this case, there is the Quarto edition (Q) of 1594 that was given the title The First Part of the Contention Betwixt the two Famous Houses of York and Lancaster as well as the one found in the First Folio of the plays of Shakespeare (F), published in 1623, where it's titled Henry VI, Part Two. The difficulties begin with the fact that "Q is roughly a third shorter than F, and differs from it in most of its readings, even though the basic material of each scene is the same. Only a handful of passages are identical in the two texts." As a result, there are two opposing positions regarding the relationship of the two versions. The first is the belief that the Quarto version is a "reported" text, i.e. one that was put together by people involved with the production, most likely some of the actors, and with very little involvement from Shakespeare himself. The other is that both versions were written by Shakespeare, with the Folio being the result of more time and a good deal of authorial revision. Warren's findings on the subject are surprising: he finds some evidence for both sides. From this, we might perhaps conjecture that Shakespeare may have used a reported version of his own work as the basis for the finished version - a fascinating hypothesis, with many implications for understanding Shakespeare's working methods and motivations. I recommend Warren's introduction very highly, particularly since my summary is, inevitably, an over-simplification of his thoughts on the subject.