Links:
[1] http://cms.springerprofessional.de/journals/JOU=10798/VOL=2010.20/ISU=1/ART=9055/BodyRef/PDF/10798_2008_Article_9055.pdf
[2] http://library.oum.edu.my/oumlib/node/474735
[3] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194162
[4] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194163
[5] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194159
[6] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194160
[7] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194161
[8] https://library.oum.edu.my/oumlib/content/taxonomy/document-delivery/194158