1. ETH Gas Station. https://ethgasstation.info/ . Accessed 01 May 2018
2. How much does it cost to sell on eBay? https://sellercentre.ebay.co.uk/private/what-fees-youll-pay . Accessed 01 May 2018
3. Sell on Amazon - Pricing and Fees. https://services.amazon.co.uk/services/sell-online/pricing.html . Accessed 01 May 2018
4. Total Retail 2017. https://www.pwc.com/gx/en/industries/assets/total-retail-2017.pdf . Accessed 01 May 2018
5. Ethersphere/swarm, December 2017. https://github.com/ethersphere/swarm