As some of you may be aware, in Thousand Suns, I sometimes use words and phrases from the constructed language of Esperanto as stand-ins for the futuristic universal human language of Lingua Terra (a name cribbed from H. Beam Piper). This not only felt "right," since a lot of Golden Age SF uses Esperanto in a similar fashion, but was fun, too, since I've had a strange fascination with Esperanto since I was a teenager.
Anyway, I recently came across references to a translation of Burroughs's A Princess of Mars into Esperanto, the cover for which I've reproduced below. I'd love to find a copy of it somewhere, though I wouldn't actually be able to read it, since, despite my interest in the language, I'm far from being fluent in it. Still, I thought it was kind of cool.