aspect ratios. Commentary soundtracks The Criterion Collection's second catalog title, King Kong (1933), was the debut of the scene-specific audio commentary contained in a separate analog channel of the LaserDisc, in which American film historian Ronald Haver spoke about the production, cast, screenplay, production design and special effects. He also provides commentary on the LaserDisc editions of Casablanca (1942), Here Comes Mr. Jordan (1941), Singin' in the Rain (1952) and The Wizard of Oz (1939). Typically, the chapter-indexed commentaries are exclusive to the Criterion releases and their initial DVD reissues; they became collectors' items when the original studios reissued titles previously licensed to Criterion, regardless of whether new commentary tracks were produced. Special editions The Criterion Collection began in 1984 with the releases of Citizen Kane (1941) and King Kong (1933) on LaserDisc, the latter's source negatives courtesy of the Library of Congress. The company later became known for pioneering the "special edition" DVD concept containing bonus materials such as trailers, commentaries, documentaries, alternate endings and deleted scenes. The success of these releases established the special-edition version in the DVD business. In 2006, taking advantage of advanced film-transfer and film-restoration technologies, Criterion published higher-quality versions, with bonus materials, of early catalog titles such as Amarcord (1973), Brazil (1985) and Seven Samurai (1954). Film restoration Originally, Criterion released art, genre and mainstream movies on LaserDisc such as Halloween (1978), Ghostbusters (1984), Bram Stoker's Dracula (1992), Armageddon (1998) and The Rock (1996). Increasingly, the Criterion Collection has also focused on releasing world cinema, mainstream cinema classics and critically successful obscure films. Using the best available source materials, the company produced technologically improved and cleaner versions, such as those for The Passion of Joan of Arc (1928), M (1931), Children of Paradise (1945), The Third Man (1949), Seven Samurai (1954) and Amarcord (1973). Almost every title contains film-cleaning and film-restoration essays in the booklets, while some even have featurettes comparing the restored and unrestored images. Licenses Some previously licensed Criterion Collection titles, such as The Harder They Come (1972), are now commercially unavailable as new product, and are only available in resale (used) form. Titles such as RoboCop (1987), Hard Boiled (1992), The Killer (1989) and Ran (1985) became unavailable when their publishing licenses expired or when Criterion published improved versions, such as those for Beauty and the Beast (1946), M (1931), The Wages of Fear (1953) and Seven Samurai (1954). As of