https://etd.repository.ugm.ac.id/penelitian/detail/1326472018never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1326502018never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1326522018never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1538112018never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1561852018never1.0https://etd.repository.ugm.ac.id/penelitian/detail/1586382018never1.0