The main national railway lines into Oslo run through Akershus with many stations such as Asker , Ullensaker , Ski and LillestrÃ m. The main national railway lines into Oslo run through Akershus with many junctions and stations such as Asker , Sandvika , Ski and LillestrÃ m. Akershus includes some of the lake MjÃ sa and some of the river Glomma .