1. Council Directive 98/83/EC, European Community. http://www.nucfilm.com/standards.html.
2. Rule of the Government of the CR of March 22, 1999, Digest of Laws of CR No. 82/1999, pp. 2313–2338.
3. Rule of the Ministry of the Environment of the CR of May 29, 1997, Digest of Laws of CR No. 117/1997, pp. 2313–2376.
4. Data of the Agency for Toxic Substances and Disease Registry in the USA. http://www.atsdr.cdc.gov/tfacts3.html.
5. Rule of the Government of the CR of June 6, 1999, Digest of Laws of CR No. 178/2001, pp. 3682–3793.