"W" numbers for works are cited from: Chappell White, Giovanni Battista Viotti (1755-1824): A Thematic Catalogue of his Works (New York, 1985) . Please replace Opus numbers with "W" numbers where known - as Viotti's opus numbering is confusing; many duos are adaptions of trios or quartets, and there several different works which share the same opus number but which aren't related in this way.