The World's Work was created in 1900.
When Worlds Collide was created in 1933.
The modernists created self-contained worlds.
Worlds of the Imperium was created in 1962.
Cyan Worlds was created in 1987.
Frontier Worlds was created in 1999.
Forgotten Worlds was created in 1988.
Worlds of Tomorrow was created in 1953.
Hunter of Worlds was created in 1977.
Wizards' Worlds was created in 1989.
Different Worlds was created in 1979.
Active Worlds was created in 1995.
Seven Worlds was created in 1976.