From wikipedia
What have people who have actually read either copy said about the degree of influence Brackett had on Empire?
The exact role which Brackett played in writing the script for Empire is the subject of some dispute. What is agreed on by all is that George Lucas asked Brackett to write the screenplay based on his story outline. It is also known that Brackett wrote a finished first draft which was delivered to Lucas shortly before Brackett's death from cancer on March 18, 1978. Two drafts of a new screenplay were written by Lucas and, following the delivery of the screenplay for Raiders of the Lost Ark, turned over to Lawrence Kasdan for a new approach. Both Brackett and Kasdan (though not Lucas) were given credit for the final script.
Many reviewers[who?] believed that they could detect traces of Brackett's influence in both the dialogue and the treatment of the space opera genre in Empire.[5] However, Laurent Bouzereau, in his book Star Wars: The Annotated Screenplays, states that Lucas disliked the direction of Brackett's screenplay and discarded it. He then produced two screenplays before turning the results over to Kasdan, who did not work directly with Brackett's script at all. It is speculation if Lucas' assignment of credit to Brackett was a mere courtesy, a mark of respect for the work she had done during her illness, or a contractual obligation.[6]
Brackett's screenplay has never been officially or legally published. According to Stephen Haffner, owner of the press that printed Martian Quest: The Early Brackett, it can be read at one of two locations: the Jack Williamson Special Collections library at Eastern New Mexico University in Portales, New Mexico (but may not be copied or checked out); and the archives at Lucasfilm, Ltd. in California.
What have people who have actually read either copy said about the degree of influence Brackett had on Empire?