Workers of the world, unite!

The political slogan "Workers of the world, unite!", one of the most famous rallying cries of socialism, comes from Karl Marx's Communist Manifesto. The actual translation is more normally given as "Working men," or "Proletarians of all countries unite!" It is sometimes extended to "Workers of the world unite, you have nothing to lose but your chains", the latter part of which does not appear anywhere in the Manifesto. If anyone knows where it comes from, that'd be helpful

It is widely known and oft-quoted, and also frequently adapted, for example in The Smiths' song "Shoplifters of the world unite" or the bumper sticker[?] "Dyslexics of the world untie".