501(c) organization - Wikipediahttps://en.wikipedia.org/wiki/501(c)_organization
IRS Delays New Rules for Dark Money Groups — ProPublicahttps://www.propublica.org/article/irs-pushes-back-new-rules-for-dark-money-groups
IRS chief promises stricter rules for 'dark money' nonprofit groups – Center for Public Integrityhttps://publicintegrity.org/federal-politics/irs-chief-promises-stricter-rules-for-dark-money-nonprofit-groups/