Useful information on the differing format releases of Star Wars - from Episodes 1 to 6 and a miscellaneous section can be found here, from the informative davisdvd•com releases website:-

StarWars•com Official 1997 Changes Articles:-

SW: SE

ESB: SE

ROTJ: SE

^ via the Internet Archive’s WayBack Machine website

StarWars•com Official 2004 Changes Articles:-

SW: SE

ESB: SE

ROTJ: SE

^ via the Internet Archive’s WayBack Machine website, with…

StarWars•com Official 2004 Changes Preservation : SW : ESB : ROTJ - compiled by doubleofive

The following links have been copied in here from other older OT•com threads on the subject of the changes made to to the Original Trilogy films over the years:-

DaMovieMan’s list of changes for his STAR WARS OT DVD site, here:-

http://web.archive.org/web/20040927122506/http://free.hostdepartment.com/s/starwarstrilogydvd/main.html

The Starkiller’s Guide to the Star Wars Mono Sound Mix, here:-

http://web.archive.org/web/20160126121513/http://homepage.ntlworld.com/russdawson/mono/

Paul Ens’ Star Wars Special Edition Annotations site, here:-

http://web.archive.org/web/20041204003859/http://www.theforce.net/swse/

Sam Davatchi’s ‘Star Wars Today’ website, here:-

http://web.archive.org/web/20041208053607/http://perso.club-internet.fr/willow/Index.html