Methanediphosphonic Acid

http://www.genome.jp/dbget-bin/www_bget?drug:D04887
https://www.chemspider.com/Chemical-Structure.15308.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=50162816
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=1314368
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=43945
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL180570
https://zinc.docking.org/substances/ZINC000008015016
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/MDN
https://en.wikipedia.org/wiki/Medronic_acid