الوصول الحر: https://doaj.org/article/23b0956fa9e34e249dbb064826e20b07Test
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::648324e0635947808aa0342b834d0e5fTesthttp://europepmc.org/articles/PMC6829247Test