| − | The ethnic origin of people can be a good, but not certain, indicator of their blood type.<ref>Dean, L., ''[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=rbcantigen.chapter.ch2 Blood Group and Red Cell Antigens]'', Chapter 2, National Institute for Health: National Centre for Biotechnical Information, accessed 1 January 2008</ref> | + | The ethnic origin of people can be a good, but not certain, indicator of their blood type.<ref>Dean, L., ''[https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=rbcantigen.chapter.ch2 Blood Group and Red Cell Antigens]'', Chapter 2, National Institute for Health: National Centre for Biotechnical Information, accessed 1 January 2008</ref> |