Reykjavík: Málvísindastofnun Háskóla Íslands, 1989. — 173 p. — (Tocharian and Indo-European Studies Supplementary Series 1).
The dual category is on the decline in Tocharian, and dual forms have been mostly replaced by plural ones. All the same, a considerable number of dual forms has been preserved, especially in West Tocharian, either directly continuing Indo-European dual forms, or extended with the element B -ne, A -ip, whose status has been somewhat disputed. In his monograph on the Tocharian system of numerals, Krause (1954: 1-12) suggested that this element was the marker of a special number category, the parai, which served to characterize natural pairs, such as the eyes, ears, feet, etc., rather than any occasional pair for which dual forms were reserved.