languages are closely related to the Yeniseian languages, but he denies any genetic relationship of the former three to Haida. Vajda's ideas on the relationship of Athabaskan–Eyak–Tlingit and Yeniseian have found support independently in works of various authors, including Heinrich K. Werner or Merritt Ruhlen. DNA analyses have not shown any special connection between the modern Ket population and the modern speakers of the Na-Dené languages. In 1996, John D. Bengtson added the Vasconic languages (including Basque, its extinct relative or ancestor Aquitanian, and possibly Iberian), and in 1997 he proposed the inclusion of Burushaski. The same year, in his article for Mother Tongue, Bengtson concluded that Sumerian might have been a remnant of a distinct subgroup of the Dené–Caucasian languages. However, two other papers on the genetic affinity of Sumerian appeared in the same volume: while Allan R. Bomhard considered Sumerian to be a sister of Nostratic, Igor M. Diakonoff compared it to the Munda languages. In 1998, Vitaly V. Shevoroshkin rejected the Amerind affinity of the Almosan (Algonquian-Wakashan) languages, suggesting instead that they had a relationship with Dené–Caucasian. Several years later, he offered a number of lexical and phonological correspondences between the North Caucasian, Salishan, and Wakashan languages, concluding that Salishan and Wakashan may represent a distinct branch of North Caucasian and that their separation from it must postdate the dissolution of the Northeast Caucasian unity (Avar-Andi-Tsezian), which took place around the 2nd or 3rd millennium BC. Evidence for Dené–Caucasian The existence of Dené–Caucasian is supported by: Many words that correspond between some or all of the families referred to Dené–Caucasian. The presence in the shared vocabulary of words that are rarely borrowed or otherwise replaced, such as personal pronouns (see below). Elements of grammar, such as verb prefixes and their positions (see below), noun class prefixes (see below), and case suffixes that are shared between at least some of the component families. A reconstruction of the sound system, the basic parts of the grammar, and much of the vocabulary of the macrofamily's most recent common ancestor, the so-called Proto-Dené–Caucasian language. Potential problems include: The somewhat heavy reliance on the reconstruction of Proto-(North-)Caucasian by Starostin and Nikolayev. This reconstruction contains much uncertainty due to the extreme complexity of the sound systems of the Caucasian languages; the sound correspondences between these languages are difficult to trace. The use of the reconstruction of Proto-Sino-Tibetan by Peiros and Starostin, parts of