1. ADL – Advanced Distributed Learning. (2008). ADL Guidelines for Creating Reusable Content with SCORM 2004. Available http://www.adlnet.gov/wpcontent/uploads/2011/07/ADL_Guidelines_Creating_Reusable _Content.pdf
2. A theory of metadata enriching and filtering: Challenges and opportunities to implementation.;G.Alemu;Qualitative and Quantitative Methods in Libraries,2016
3. Reusable Objects: Learning Object Creation Cycle
4. Beyene, W.M. (n.d.). Metadata and universal access in digital library environments. Academic Press.