DeLancey, Virginia (2015). "Unions"(PDF). In Berry, LaVerle (ed.). Sudan : a country study (5th ed.). Washington, D.C.: Federal Research Division, Library of Congress. pp. 169–171. ISBN978-0-8444-0750-0. This article incorporates text from this source, which is in the public domain. Though published in 2015, this work covers events in the whole of Sudan (including present-day South Sudan) until the 2011 secession of South Sudan.{{cite encyclopedia}}: CS1 maint: postscript (link)