The New Grove Dictionary of Jazz is a particularly important reference source.  We have both print and online versions of it. The online version is integrated into Grove Music Online, which is one of the databases we subscribe to from Oxford Music Online: 
Grove Music Online

The print volumes are on the Music Reference shelves.
The latest print edition has this call number:
ML102.J3 N48 2002 (3 volumes)
The two earlier print editions have these call numbers:
ML102.J3 N48 1994  
ML102.J3 N48 1988 (2 volumes).

CAUTION: Although the New Grove Dictionary of Jazz has been integrated into Grove Music Online, not all of the articles from the print volumes are included there. This could affect your research. For example, it might mean that if you look up a certain jazz artist or certain term in each print edition, you would find different articles by different authors, none of which are in the online version. 

We have many print jazz discographies; they are on the music reference shelves. Several, but not all, are under call number ML 156.4

An important example is The Jazz Discography by Tom Lord, a multi-volume work under call number ML156.4.J3 L67 1992

We have the online version. To access it, search it in our online catalog: discover.library.unt.edu
or click the following link to go directly to the catalog entry for it:

Jazz Discography