Since your post is blank, we can't know what you meant to say or what you were asking for but there's a long entry about it on Wiki -the Spanish entry is muuuuuch more documented. The song was composed by Sergio Ortega and written by him and the Quilapayún (Cf. there) in 1973.

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You caught me, Monique. My post was blank. I was tricking Mudcat into accepting special formatting...
I'd like to know more about the song, if you have anything. Thanks. -Joe-