Thanks very much for this. I read a small collection of these stories as a kid, sometime back in the '60s. Looking forward to rereading them.
It appears to me that this collection, selling for $0.99 on amazon, has been ripped off from here:
http://www.amazon.com/The-Thinking-M.../dp/B0038BRJIO
In the preview, everything but the cover looks identical.