Carbon 14 Urea

http://classyfire.wishartlab.com/tax_nodes/C0000000
http://classyfire.wishartlab.com/tax_nodes/C0000264
http://classyfire.wishartlab.com/tax_nodes/C0000364
http://classyfire.wishartlab.com/tax_nodes/C0000517
http://classyfire.wishartlab.com/tax_nodes/C0000517
http://classyfire.wishartlab.com/tax_nodes/C0004557
http://classyfire.wishartlab.com/tax_nodes/C0000278
http://classyfire.wishartlab.com/tax_nodes/C0003940
http://classyfire.wishartlab.com/tax_nodes/C0004150
http://classyfire.wishartlab.com/tax_nodes/C0001831
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=11457650
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=347827870
https://www.chemspider.com/Chemical-Structure.9632491.html
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=253158
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=134711
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL2096635
https://www.drugs.com/pro/pytest.html
https://en.wikipedia.org/wiki/Urea_breath_test