Original sentence: The only exception was Yeniseian, which has since been shown to be related to the Na-Dené languages of North America (Vajda 2008)
Edited sentence: The only exception was Yeniseian, which has been related to the Na-Dené languages of North America in a Dené-Yeniseian family by Edward Vajda as well as a wider Dené-Caucasian grouping by other linguists