| Author's List |
| title | creator | language | description | tableOfContents | contributor | subject | created |
| Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" | Various | en | 2006-11-17 | ||||
| The Balkans A History of Bulgaria—Serbia—Greece—Rumania—Turkey | en | 2004-03-01 | |||||
| Area Handbook for Bulgaria | en | 2010-05-31 | |||||
| Bulgaria | Fox, Frank, Sir, 1874-1960 | en | 2007-08-06 | ||||
| Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" | Various | en | 2006-11-02 |