Check the following:
Grove:
[Mus Ref Book ML100 .N48 2001]
The New Grove dictionary of music and musicians. 2nd edition. London : Macmillan Publishers; Washington, D.C. : Grove's Dictionaries of Music, 2001. 29 volumes.
Grove Music Online updates the full text of The New Grove Dictionary of Music and Musicians, 2nd edition, The New Grove Dictionary of Opera, (London, 1992), and The New Grove Dictionary of Jazz, 2nd edition, (London, 2002). It also includes access to Oxford Music reference tools.
For this project, look for the Editions statement at the beginning of the Works list at the end of an article about a specific composer.
Example: Bach, Johann Sebastian Grove Music Online article
You can also find the Edition statement at the beginning of the Works list at the end of an article about a specific composer in the published edition of Grove:
WorldCat database
Since Grove is not always up-to-date, do the following search in the WorldCat database to make sure you get all recent collected works:
Author (au:): “composer's last name, first name”
Uniform title (ut:): “Works”
Limit by year [a dialog box]: “1997-”
Put a check by "musical scores"
Results can be sorted by year by selecting "sort" at the upper left hand side. Choose "Date" as the sort criteria.
Vassar College holdings are denoted by the following green icon:
VASSAR COL