URL الوصول: https://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-70375https://lnu.diva-portal.org/smash/get/diva2:1179494/FULLTEXT01.pdf
URL الوصول: https://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-46013
URL الوصول: https://lup.lub.lu.se/record/7357550http://dx.doi.org/10.1016/j.econedurev.2015.01.008