Complex sentence: On 16 November 1961, the municipal committee of former partisans from Bosanska Dubica organized an unofficial investigation at the grounds of Donja Gradina, led by the locals who were not forensic experts, which uncovered three mass graves and identified 17 human skulls in one of them.
Split into simpler sentences: On 16 November 1961, the municipal committee of former partisans from Bosanska Dubica organized an unofficial investigation at the grounds of Donja Gradina, led by locals who were not forensic experts. This investigation uncovered three mass graves and identified 17 human skulls in one of them.