Who Is The Artist?

Another request for information. Can anybody identify the artist who did the covers for these four Ballantine (not Del Rey!) editions of works by Arthur C. Clarke?

Scroll down to Expedition to Earth.

Scroll down to Tales from the White Hart.

Scroll down to Earthlight.

Scroll down to Reach for Tomorrow.

I've got all four myself and none have any artist credits in the usual places, even a signature that I can find on the artwork itself. I remember this set fondly, as a 6th or 7th grade English teacher had all four in her class and loaned them to me.