URL الوصول: https://library.oapen.org/handle/20.500.12657/74738
URL الوصول: https://library.oapen.org/handle/20.500.12657/50822
URL الوصول: https://library.oapen.org/handle/20.500.12657/60940
URL: https://www.ssoar.info/ssoar/handle/document/85263https://www.transcript-verlag.de/shopMedia/openaccess/pdf/oa9783839456736.pdfhttps://doi.org/10.14361/9783839456736