Collected works are sets of printed music of one composer’s complete works. The titles of these collected sets are often in the original language of the composer such as:
Collected Editions are very useful as a source for locating a work not available as individual score in the library collection. You can find them by browsing the M3 scores.
You can locate individual items in a composer's collected works using the Grove Music Online database .
Here is as section from the article on Johannes Brahms.