Hydra

http://classyfire.wishartlab.com/tax_nodes/C0000000
http://classyfire.wishartlab.com/tax_nodes/C0000264
http://classyfire.wishartlab.com/tax_nodes/C0002285
http://classyfire.wishartlab.com/tax_nodes/C0002285
http://classyfire.wishartlab.com/tax_nodes/C0004557
http://classyfire.wishartlab.com/tax_nodes/C0000323
http://classyfire.wishartlab.com/tax_nodes/C0000117
http://classyfire.wishartlab.com/tax_nodes/C0004150
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:44423
http://metacyc.org/META/new-image?type=COMPOUND&object=HYDROXY-UREA
http://www.hmdb.ca/metabolites/HMDB0015140
http://www.genome.jp/dbget-bin/www_bget?drug:D00341
http://www.genome.jp/dbget-bin/www_bget?cpd:C07044
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=3657
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46506927
https://www.chemspider.com/Chemical-Structure.3530.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=50017811
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=5552
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=44423
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL467
https://zinc.docking.org/substances/ZINC000008034120
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP000739
http://www.pharmgkb.org/drug/PA449942
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/NHY
http://www.rxlist.com/cgi/generic2/hydroxyurea.htm
https://www.drugs.com/cdi/hydroxyurea.html
https://en.wikipedia.org/wiki/Hydroxycarbamide