1. DIRECTIVE 2003/4/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 28 January 2003 on public access to environmental information and repealing Council Directive 90/313/EEC.
https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2003:041:0026:0032:EN:PDF
. Accessed 04 Dec 2019
2. Riley, J.: NISO: Understanding Metadata (2017).
https://groups.niso.org/apps/group_public/download.php/17443/understanding-metadata
3. Alemu, G., Stevens, B.: An Emergent Theory of Digital Library Metadata - Enrich then Filter. Chandos Information Professional Series. Elsevier, Amsterdam (2015)
4. Haslhofer, B., Klas, W.: A survey of techniques for achieving metadata interoperability. ACM Comput. Surv. (CSUR) 42(2) (2010).
http://eprints.cs.univie.ac.at/79/1/haslhofer08_acmSur_final.pdf
5. ISO 19115-1:2014: Geographic information—Metadata—Part 1: Fundamentals. ISO standard, International Organization for Standardization (2014)