King's Indian Attack

I guess u mean this variation?

But there are many other lines u know... And thats just the beginning here...

https://www.chess.com/article/view/has-the-king-s-indian-attack-been-forgotten

The KIA is discussed in Winning Chess Openings by GM Yasser Seirawan (1999).
https://web.archive.org/web/20140627132508/http://www.chesscafe.com/text/hansen173.pdf
For more on the KIA, one could try The King's Indian Attack: Move by Move by Grandmaster Neil McDonald (2014).
https://www.newinchess.com/media/wysiwyg/product_pdf/7277.pdf
Perhaps, it would be of interest to look at The Fianchetto Solution by Emmanuel Neiman and Samy Shoker (2016)
https://www.newinchess.com/media/wysiwyg/product_pdf/9029.pdf
and Starting Out: King's Indian Attack by John Emms (2005).
https://web.archive.org/web/20140627034051/http://www.chesscafe.com/text/hansen81.pdf

 https://www.chess.com/article/view/has-the-king-s-indian-attack-been-forgotten

I do not believe there is a main variation in the KIA. I however do believe that there is definitely a main setup. Black has many different lines he/she can try, but the White player will generally always go for this same setup:

The fact that Black has many different paths to choose from (most of which are arguably equal; in other words, there is no one line that is best for Black--what Black does is a matter of taste) negates the idea of the KIA having a main variation. However, as stated above, the KIA vs. the French Defense variation is probably the most well-known KIA line. This does not necessarily mean it is the "main line," though.