This one looks interesting. It's listed at Amazon. http://www.velikovskian.com/sagan.htm
I found the whole business a bottomless pit when I read V's books + criticisms in the early 70s. Sagan hadn't burst onto the scene at the time. Things may be a bit clearer 35 years later, not necessarily because of Sagan's efforts. Good luck.
"Billions and Billions"
