Answer the following question: Extract the answer to the question from the following context. Question: Whose model was the BPF based on? Context: The Partyja BPF (Belarusian Popular Front) was established in 1988 as a political party and cultural movement for democracy and independence, a la the Baltic republics' popular fronts. The discovery of mass graves in Kurapaty outside Minsk by historian Zianon Pazniak, the Belarusian Popular Front's first leader, gave additional momentum to the pro-democracy and pro-independence movement in Belarus. It claimed that the NKVD performed secret killings in Kurapaty. Initially the Front had significant visibility because its numerous public actions almost always ended in clashes with the police and the KGB.
Answer:
the Baltic republics' popular fronts