الإتاحة: https://doi.org/20.500.12627/63872Testhttps://hdl.handle.net/20.500.12627/63872Test
الإتاحة: https://doi.org/20.500.12627/11949Testhttps://doi.org/10.1183/1393003.congress-2017.oa4842Testhttps://hdl.handle.net/20.500.12627/11949Test