Old English, ca. 450-1100 501
Ottoman Empire, 1288-1918 238
Occupation, 1939-1945 72
Old High German, 750-1050 58
Opium War, 1840-1842 45
Ordovician 39
Occupation, 1941-1944 21
Oligocene 13
Orange Revolution, 2004 12
Obras anteriores a 1800 11
October Crisis, 1970 11
Old Kingdom, ca. 2686-ca. 2181 B.C. 8
October Revolution, 1944 4
Otto I, 936-973 4
Overthrow of the Monarchy, 1893 4
Obras tempranas hasta 1800 2
Occupation, 1941-1945 2
Obras anteriores al S XVIII 1
Obras hasta 1800 1
Occupation and evacuation, 1871-1873 1
Octava region 1
Ocupacion britanica, 1765-1947 1
Ordovicico 1
Otho I, 1832-1862 1