How do you find the missing feathers in Assassins Creed II

This is the toughest thing to do in the game (in my opinion).
There are many maps available to help you, but the trouble I have is that running through the game I was able to find about 60 of them, but now I have no idea which 40 I missed, and I do not think there is a way to do so. You're going to have to run through each map area, and using some guide online (just google it, there are plenty of guides out there) check each point; even if you already got that feather (unless you remember where every feather you got was, which is unlikely)... Hopefully you and aren't missing 1 or 2 when you're done or else you'll have to do the whole thing over.

I suggest trying to use eagle vision when you get close to the area it says; the feathers will glow white.