https://etd.repository.ugm.ac.id/penelitian/detail/946362016never1.0https://etd.repository.ugm.ac.id/penelitian/detail/961362016never1.0https://etd.repository.ugm.ac.id/penelitian/detail/962312016never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1021572016never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1026502016never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1057862016never1.0