Zeta

Zeta was a letter in the Greek language alphabet of Earth, originating in the early period of human history.

It was used in the following contexts:

Doctor Who Universe

 * Zeta Minor (DW: Planet of Evil)
 * Zeta Cancri (AK9: K9 and the Zeta Rescue)
 * Zeta Reticuli Four (NA: First Frontier)

Behind the scenes

 * Zeta Major, a BBC Past Doctor Adventures Novel
 * K9 and the Zeta Rescue, a book in The Adventures of K9 series
 * Project Zeta Sigma, an unproduced serial that would have been the first story of the Fifth Doctor (REF: Doctor Who - The Handbook: The Fifth Doctor)