Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 416, 860–861. doi:10.1039/9781849733069-FP001. ISBN978-0-85404-182-4. The compound H2N-CO-NH2 has the retained named ‘urea’, which is the preferred IUPAC name, (…). The systematic name is ‘carbonyl diamide’.