الوصول الحر: https://doaj.org/article/19bac9f2b1c94b5f812ac69d4aaead70Test
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3c655b0a8c6e42df2c378d44ab040635Testhttp://www.sciencedirect.com/science/article/pii/S2351989420307939Test