original: at that time , the area contained the greta swamp , which was later drained .
simplifications: at that time the area contained the grete swamp . at that time , the greta area having swamp , which was drained later . at that time the area contained the greta swamp which later drained . at that time , the area contained the greta swamp , which was later drained . at that time , the area contained the greta swamp , which was later drained . at that time , the area had within the greta swamp , which was later drained . the area contained the greta swamp , which was later drained . the area contained the greta swamp was drained .