U.S. Customs and Border Protection
Website https://www.cbp.gov/
Email CBPMEDIARELATIONS@cbp.dhs.gov
Phone (202) 344-1780

U.S. Immigration and Customs Enforcement
Website: https://www.ice.gov/
Email ICEMedia@ice.dhs.gov
Phone (202) 732-4242

Congressional Research Service brief on “Executive Authority to Exclude Aliens” https://fas.org/sgp/crs/homesec/R44743.pdf

Pew Research Center research on immigration: http://www.pewhispanic.org/2016/09/20/overall-number-of-u-s-unauthorized-immigrants-holds-steady-since-2009/