ChemSpiderA free structure database from the Royal Society of Chemistry, with millions of substances linked to freely available data from sources like PubMed and PubChem, RSC publications, and ChemIDPlus (NLM), as well as publicly available data from GlaxoSmithKline, National Institutes of Health (NIH), National Institute of Standards and Technology (NIST), and Sigma-Aldrich, as well as data supplied by researchers.