Old Distributions?

rsd writes: "I have been searching the web for a few days looking for old rpm based distributions ISOs for a study with libc5. All I could find so far is some loose packages, but not a downloadable ISO image. For RedHat 4.2 and older, Conectiva Linux 1.0, ... it is impossible to find. So I ask myself is there a centralized place taking care of this, for public use and even preservation of the Linux History and evolution? We have lots of places with ISO images, like linuxiso, however these sites just keep with recent distributions."