In the "For What It's Worth" column: As some here have posted, who's responsible for the script of TWOK is far more complicated than just arguing about Bennett and Sowards.
The evolution of the story as it's related in Memory Alpha is interesting for those who weren't aware of it (or those who need their memories jogged).
Bennett came up with the original idea for the story and wrote a treatment that he gave to Sowards to turn into a screenplay. After the first draft, many people contributed criticisms and ideas in moving towards the final script, even though Sowards remained the sole credited screenwriter. Samuel Peeples and Nicholas Meyer had especially strong influences on the final screenplay, though they were uncredited.
Link to story (scroll about half-way down the page to the heading, "Background Information"):