The PubMed platform contains MEDLINE, PubMed Central, and additional PubMed records, and indexes journal articles and more back to 1947. It covers medicine, nursing, dentistry, veterinary medicine, health care systems, preclinical sciences, and related areas. It is developed and maintained by the National Library of Medicine (NLM) and the National Center for Biotechnology Information (NCBI), both at the National Institutes of Health (NIH) in the US. As of December 2020, PubMed contains over 30 million records. Links to full text content of items indexed in PubMed are usually available via Library Search, publisher websites or library interlibrary loan.