http://www.computerandvideogames.com/article.php?id=97911
http://www.totalvideogames.com/Gran-Turismo-4/news/GT4-For-Christmas-4489.html
These we're the best links I could come up with. In 2003 was set to be released in christmas time, but then got delayed for another year, which resulted in a prologue version in 2004 which was originaly planed to be japan only. Then in 2004 EU and NA got the prologue version as well, but had to wait yet another year for the full release of the game.
I remember at that time being sad that GT4 was taking up so long to be released, especially since they had already released GT3 in the PS2, so 4 years in the making of a game with the same technology, wasn't making much sense, until the features for the game were announced, and it had tripled almost everything GT3 had offered.
http://cars.ign.com/articles/535/535460p1.html
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