Which authors have had the most film / TV series adaptions?

I hope it's okay to post this here. I have watched a number of Sci-Fi dystopian films and noticed that many of them have been based on novels or short stories.

I have only read the following works so far:

  • I Have No Mouth,  and I Must Scream by Harlan Ellison
  • Do Androids Dream of Electric Sheep? by Philip K. Dick
  • R.U.R by Karel Capek
  • Brave New World by Aldous Huxley
  • 1984 by George Orwell
  • Fahrenheit 451, by Ray Bradbury

I want to know which authors of Sci-Fi have had the most adaptations in film and or TV series?