- “Alexander I., Prince of Bulgaria,” from Men of the Time, eleventh edition (1884)
- “Bulgaria” in The Nuttall Encyclopædia by James Wood, London: Frederick Warne and Co., Ltd., 1907.
- “Bulgaria,” in Encyclopædia Britannica, (11th ed.), 1911
- “Bulgaria,” in Catholic Encyclopedia, New York: The Encyclopaedia Press (1913)
- “Bulgaria,” Encyclopædia Britannica (12th ed.), 1922.
- “Bulgaria” in The World Factbook by the CIA, 1982.
- “Bulgaria” in The World Factbook by the CIA, 1990.
- “Bulgaria” in The World Factbook by the CIA, 2004.
- Oscar Wilde, “On the Massacre of the Christians in Bulgaria”
- Great Battles of Bulgaria
- Bulgarian Policies on the Republic of Macedonia
- Essential History of Bulgaria in Seven Pages
- Treaty of Conciliation between Bulgaria and the United States of America
- Charter ’89 for Preservation of the Bulgarian Nature Heritage
- Treaty Of Friendship And Alliance Between Bulgaria And Serbia
- Bulgarian Declaration of Independence, 1908
- Bulgarian Policies on the Republic of Macedonia, 2008 by Lyubomir Ivanov
- The Truth About Bulgaria, 1919 by Athanasious Toleff Christoff
- The Aspirations of Bulgaria, 1915 by Stojan M. Protic
- With Gypsies in Bulgaria, 1915 by Robert Andrew Scott Macfie