Adsense … http://www.seroundtable.com/archives/019808.html
SEOed site vs Quality site … http://www.webmasterworld.com/google/3889779.htm
20% to 25% of search queries are unique … http://www.seobook.com/most-seo-strategies-are-not-focused-hitting-home-runs
How to use curl_multi() without blocking … http://www.onlineaspect.com/2009/01/26/how-to-use-curl_multi-without-blocking/