Cystine

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:16283
http://www.hmdb.ca/metabolites/HMDB0000192
http://www.genome.jp/dbget-bin/www_bget?drug:D03636
http://www.genome.jp/dbget-bin/www_bget?cpd:C00491
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=67678
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46506670
https://www.chemspider.com/Chemical-Structure.60997.html
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=3036
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=16283
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL590540
https://zinc.docking.org/substances/ZINC000001532673
http://www.pharmgkb.org/drug/PA449176
http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/lcy_0088.shtml
https://en.wikipedia.org/wiki/Cystine