User blog comment:Darkcloud1111/''The Mark of Athena'' Plot Holes/@comment-66.177.180.197-20121213223148/@comment-3146930-20121213223829

From what I understand, it really depends on where you bought the book. For example, the copy I have says "Gaea" and my copy was bought in America. There was one use from the Philippines (I think he was from there) who's book had it spelled Gaia. While both spellings are correct, because Rick Riordan is an American author, we use the spelling that is in the American copy.