https://etd.repository.ugm.ac.id/penelitian/detail/2285922012never1.0https://etd.repository.ugm.ac.id/penelitian/detail/2286692012never1.0https://etd.repository.ugm.ac.id/penelitian/detail/2286702012never1.0https://etd.repository.ugm.ac.id/penelitian/detail/2288332012never1.0https://etd.repository.ugm.ac.id/penelitian/detail/2293672012never1.0