That is Google said about (Referral Ads Retirement)

"What happened to referrals?

During the last week of August, the AdSense referrals feature will be retired for both AdWords advertiser products and Google products. After careful consideration, we believe that we can best serve our advertisers and publishers through two alternative offerings, AdSense for content and DoubleClick Performics Affiliate.

Beginning in late August, any remaining referral ads on your site will no longer work, and will appear as blank space on your website. In order to prevent a decrease in your AdSense earnings, we strongly encourage you to replace all referral ad code on your sites with AdSense for content ad code prior to the last week of August. You can get this ad code by signing in to your AdSense account, selecting the AdSense Setup tab, and choosing AdSense for content as the product.

If you'd prefer to manually select the ads that appear on your website in the future, we encourage you to check out DoubleClick Performics Affiliate.

For More Informations Visit Google Help Centre"