Optimal

http://www.hmdb.ca/metabolites/HMDB0001852
http://www.genome.jp/dbget-bin/www_bget?drug:D00094
http://www.genome.jp/dbget-bin/www_bget?cpd:C00777
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5538
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46504843
https://www.chemspider.com/Chemical-Structure.392618.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=31883
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=10753
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=15367
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL38
https://zinc.docking.org/substances/ZINC000012358651
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DNC000117
http://www.pharmgkb.org/drug/PA164746900
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/REA
http://www.rxlist.com/cgi/generic/tretinoin.htm
https://www.drugs.com/cdi/tretinoin.html
https://en.wikipedia.org/wiki/Tretinoin