الوصول الحر: https://gup.ub.gu.se/publication/335377Test
الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::31d0f111006319341743575a0031db62Testhttps://ora.ox.ac.uk/objects/uuid:cc37fff7-fb18-4677-9915-24e6ba021aafTest
الإتاحة: https://doi.org/10.1016/S0140-6736Test(19)31997-Xhttps://orbi.uliege.be/handle/2268/250399Test