Original: Akershus became a fief in the 16th century, and then also included the current counties of Hedmark, Oppland, Buskerud and Oslo, as well as the municipalities of Askim, Eidsberg and Trøgstad in the county of Østfold.
Simplified: Akershus became a fief in the 16th century. It also included municipalities of Askim, Eidsberg and Trøgstad in the county of Østfold.