Citing a screenplay is different from citing a film. The text of a screenplay that you consult will have its own authors and publication information. There is no need to provide information about the film itself, such as its director or the studio that produced it. Just be sure to make it clear that you are citing the screenplay and not the film, since the two might have the same title. If you consult the screenplay in a published edition, the title will usually be clear enough, as it is in the following example:

Welles, Orson, and Herman J. Mankiewicz. Citizen Kane: The Complete Screenplay. Methuen Publishing, 2002.

However, sometimes it will not be clear that the title in your works-cited-list entry refers to the screenplay and not the film. In that case, you could do one of two things. You could provide a generic description in place of the title, as the following example shows:

Welles, Orson, and Herman J. Mankiewicz. Screenplay of Citizen Kane. Daily Script, www.dailyscript.com/scripts/citizenkane.html.

Or you could use the final optional-element slot to indicate that what you are citing is a screenplay. The following provides an example:

Welles, Orson, and Herman J. Mankiewicz. Citizen Kane. Daily Script, www.dailyscript.com/scripts/citizenkane.html. Screenplay. 

See also our related posts on citing the script and performance of a play and on citing a film based on a book.