In addition to the Music Library's print music holdings, there are other online resources for musical scores that may include works featuring the viola.
In addition to scores of musical works featuring the viola (found in call number areas outlined within the Overview tab), orchestral studies and excerpts for the viola are available in the Music Library (in call number area MT 286).
Gentz, August, ed. Orchesterstudien aus seinen Bühnenwerken [for] viola: Richard Stauss.
MT 286 .S92 1987
Showell, Jeffrey, ed. A solo folio for the principal violist.
MT 286 .S69 198-