• http://repository.ou.ac.lk/handle/123456789/4253
• http://repository.ou.ac.lk/handle/123456789/4254
• http://repository.ou.ac.lk/handle/123456789/4256
• http://repository.ou.ac.lk/handle/123456789/4240
• http://repository.ou.ac.lk/handle/123456789/4241
• http://repository.ou.ac.lk/handle/123456789/4246
• http://repository.ou.ac.lk/handle/123456789/4258