المصدر: Bibliotheca Alexandrina (2011)؛ وUniversity of Maryland (2011)؛ وThomson Reuters (2006)؛ وCRDF Global (2011)؛ وEuropean Commission (2006).
资料来源：Bibliotheca Alexandrina (2011)；University of Maryland (2011)；Thomson Reuters (2006)；CRDF Global (2011)；European Commission (2006)