it was their parliament that declared independence for Kosovo, not a referendum
You had a fcuked up your history class. It all started when Tito let some Albanian migrants into Kosovo to live. Gradually (purely for a better life and in an attempt to escape Albanian poverty) more and more of them trickled in. Then these migrants and their descendants started to pull the blanket over themselves - and Serbs started to get fed up with it. But a critical mass had already accumulated and process was began....
On September 22, 1991, the migrant Albanian community declared the creation of an independent Republic of Kosovo, and then an unsanctioned (only among the Albanian community, the historical owners of the land were fcuked) referendum on independence was held (99% of those who voted with a turnout of 87% voted for independence) and presidential elections, during which Ibrahim Rugova was elected president.
Serbs tried to object, but NATO came to the rescue, a cozy little backwater where drugs are sold and people and stolen cars are dismantled for organs was useful to them. You can launder almost any amount of money.
As a result, Serbs were kicked by the crowd, and Kosovo became a precedent, and now Westerners will be periodically fcuked up for this precedent, like now with Ukraine.