You can find three types of scores in the Reference section:
How to Find Compositions within Complete Works & Historical Sets
Collected Works and Historical Sets are often organized in multiple volumes and series. Some are as simple as volumes 1, 2, 3, etc., while others are more complicated with series, sub-series, and volumes within the sub-series:
For example, this is how the first portion of Mozart's Neue Ausgabe (New Collected Works) is organized:
Thematic Catalogues are detailed lists (or catalogues) of a composer's entire output. They are organized either chronologically or by opus number and include information about manuscripts, premieres, where the composition can be found in the composer's Complete Works, incipits (or music examples) of major musical themes, and other useful information.
Browse Ref ML 134 to see what print Thematic Catalogues Queens College has!
Online Thematic Catalogues