Turchin, Peter; Adams, Jonathan M.; Hall, Thomas D (December 2006). "East-West Orientation of Historical Empires". Journal of World-Systems Research. 12 (2): 223. ISSN 1076-156X. Retrieved 16 September 2016.
^ Rein Taagepera (September 1997). "Expansion and Contraction Patterns of Large Polities: Context for Russia". International Studies Quarterly. 41 (3): 493. doi:10.1111/0020-8833.00053. JSTOR 2600793. Retrieved 7 September 2018.
^ Reynolds, Frank. "Angkor". Encyclopædia Britannica. Encyclopædia Britannica, Inc. Retrieved 17 August 2018.
^ Plubins, Rodrigo. "Khmer Empire". Ancient History Encyclopedia. Ancient History Encyclopedia. Retrieved 17 August 2018.