Tracking Conversion Across Multiple Domains

[pro_seo]

Hello Friends,

I have a site abc.com which acts as a central buying site for, lets say products A, B and C.

Now there are separate sites solely on the products, like A.com; B.com and C.com. From each of these sites when an order is to be placed, the user gets redirected to abc.com.

For example - If someone visits A.com and wants to buy the product, on clicking "Buy Now" he gets redirected to abc.com/buy-a.html from where he can add the products to his cart and eventually can checkout.

Now I am unable to track the conversion rates of how many people are coming in to abc.com from each of the domains A.com, B.com etc and how many are actually making purchases.

I want to track this conversion. Plzzz help me on this.

Thanks a lot in advance :)

[pro_seo]

Come on friends....not a single reply?