http://www.propublica.org/blog/item/what-the-goldman-sachs-settlement-means-in-context 
Goldman’s SEC Settlement by the Numbers: We Do the Math

http://www.zerohedge.com/article/its-not-market-its-hft-crop-circle-crime-scene-further-evidence-quote-stuffing-manipulation-

"It's Not A Market, It's An HFT 'Crop Circle' Crime Scene" - Further Evidence Of Quote Stuffing Manipulation By HFT