Elton, Lord
Imperial commonwealth
Collins, 1945
 Buku Teks SO
Loewe, Michael
Imperial China
Frederick A. Preager, 1965
 Buku Teks SO
Hadas, Moses
Imperial Rome
Time-Life Books, 1965
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Mitchell, Richard H.
Censorship in imperial Japan
Princeton University Press, 1983
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Tacitus, Cornelius
The annals of imperial Rome
Penguin Books, 1956
 Buku Teks SO