<https://www.thebalancecareers.com/hobbyist-vs-pro-tax-guidelines-for-book-authors-2799859>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.thebalancecareers.com/hobbyist-vs-pro-tax-guidelines-for-book-authors-2799859>