الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::27cb5c2c653f4b45b5a87287bc68f231Test
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::d04c831d78c41551246ba99cf2e059dfTesthttps://doi.org/10.1016/s0304-405xTest(98)00057-9
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::cf89caf7b938db7694f1cac980ddf0f8Test
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=od_______645::3e17c8e56907a3b3162a533615672b8bTesthttp://purl.umn.edu/20691Test