First, don't restrict yourself to library databases. Primary source collections are often found free online, depending on the subject you are researching.
Second, when you use library databases you will get limited results if you try to search for "primary sources" because the Library of Congress does not use that subject heading. If a "Primary Sources" category is not available (JSTOR provides one that is very useful!) Try searching these subject headings instead:
SOME ADVICE ON AUTOBIOGRAPHIES: You will get limited results searching for the word "autobiography" since the Library of Congress does not use that subject heading. Try searching for "biography" but then look to make sure that the author is also listed as a subject. That is your clue that the person is writing about him or herself, and that is a primary source.
DOCUMENTARY HISTORIES: There are collections of documents relating to various subjects, such as Agriculture in the United States: A Documentary History. Search WorldCat or IDS for these by typing your subject along with the phrase "documentary history" in quotes.
DOCUMENTARY FILMS: Be wary of "documentaries" (films) because sometimes they are primary sources but sometimes they provide analysis that is secondary.
PUBLICATION DATES: Be aware that publication dates can be misleading. A new edition of a book published in 1952 is still a primary source even though its publication date is 2009. Look for a books original publication date, which is usually listed as well.
Some scholarly journals that cover the Balkans:
Balkanistica
Bulgarian Historical Review
Contemporary European History
East European Politics & Societies
Ethnic & Racial Studies
Europe-Asia Studies
European History Quarterly
International Journal of Middle East Studies
International Journal of Turcologia
Journal of Balkan & Near Eastern Studies
Journal of Genocide Research
Journal of Muslim Minority Affairs
Journal of Southeast European & Black Sea Studies
Middle Eastern Studies
Nationalism & Ethnic Politics
Nationalities Papers: Journal of Nationalism and Ethnicity
Slavic Review
Southeastern Europe
Turkish Studies
You will certainly find books by searching the research databases for "the Balkans" or the "Balkan Peninsula," but because of the geopolitical changes in the area, remember to be specific when you can be.
Countries wholly in the Balkans:
Albania (capital and largest city: Tirana)
Bosnia and Herzegovina (capital and largest city: Sarajevo)
Bulgaria (capital and largest city: Sofia)
Kosovo (capital: Pristina)
Macedonia (capital and largest city: Skopje)
Montenegro (capital: Podgorica)
Countries partly in the Balkans:
Croatia (capital and largest city: Zagreb)
Greece (capital and largest city: Athens)
Romania (capital and largest city: Bucharest)
Serbia (capital and largest city: Belgrade)
Slovenia (capital and largest city: Ljubljana)
Turkey (capital: Ankara; largest city is Istanbul, aka Byzantium and Constantinople)
Official Library of Congress subject headings can be different than the normal names people call things. Note the following subject headings for the wars:
First Balkan War (1912–1913)
Second Balkan War (June 1913)
World War (1914-1919)
World War (1939-1945)
Source: https://www.worldbulletin.net/balkans/mother-of-srebrenica-victim-to-bury-son-after-22-years-h191691.html
Source: https://foreignpolicy.com/2017/06/28/the-hague-just-reminded-us-why-safe-zones-may-not-be-safe-syria-srebrenica-iran-russia/