Complex sentence: This account is corrobrated by "Magnúss saga lagabœtis", which states that Scottish forces invaded the Isles in the summer after Hákon's campaign, and forced the submission of Aonghus Mór and other adherents to the Norwegian cause.
Split into simpler sentences: This account is corrobrated by "Magnúss saga lagabœtis". In specific regard to Aonghus Mór, the saga states that Scottish forces invaded the Isles in the summer after Hákon's campaign, and forced the submission of Aonghus Mór and other adherents to the Norwegian cause.