Executive orders are numbered; memoranda are not. Memoranda are always published in the Federal Register after proclamations and executive orders. And under Executive Order 11030, signed by President Kennedy in 1962, an executive order must contain a "citation of authority," saying what law it's based on. Memoranda have no such requirement.http://www.usatoday.com/story/news/politics/2014/12/16/obama-presidential-memoranda-executive-orders/20191805/