City limits

Im Playing for à few weeks now,
When i occupy à oasis in getting à letter it say:

"city limits Exceed "

What does it means? And how can i occupy oasis again??

http://www.haypi.com/general.htm

You can only occupy a certain number of oases based on your level. At the bottom of the page that I linked above, it will show you how many oases/fortified points you can have per level

Since it took forever to load that page ^^^ il make a post on the basics:

For oasis: divide your level by 2 and round up

For forts: Baron = 1, Viscount = 2, Earl = 3, Marquis = 4 etc

For sub cities: Baron = 1, Viscount = 2, Earl = 3, Marquis = 4 etc