7 books in series

Time Traders/Ross Murdock

Time Traders/Ross Murdock is a 7-book series with 7 primary works first released in 1958 with contributions by Andre Norton, P.M. Griffin, and Sherwood Smith.

The Time Traders
Galactic Derelict
The Defiant Agents
Key Out of Time
Firehand
Echoes in Time
Atlantis Endgame