http://www.bna.com/quill-case-challenging-n57982070441/
https://netchoice.org/acma-netchoice-file-legal-challenge-south-dakotas-blatantly-unconstitutional-internet-sales-tax-law/
http://www.insidesalt.com/2016/04/breaking-news-sales-tax-battle-breaks-out-in-south-dakota-quills-last-stand/