https://oposicionestic.blogspot.mx/2012/08/en-1975-el-organismo-de-estandarizacion.html http://fernandoarciniega.com/modelo-ansi-sparc-ansi-park-arquitectura-de-3-niveles-bases-de-datos/ https://html.rincondelvago.com/bases-de-datos_7.html https://books.google.com.mx/books?id=Vhum351T-K8C&pg=PA33&lpg=PA33&dq=Ansi+sparc&source=bl&ots=fzI3LVga2n&sig=1DAc26Pajd8-rBQsqiuy4FbiVMs&hl=es&sa=X&ved=0ahUKEwiutbLuv8_ZAhUUXGMKHfhVC2Y4ChDoAQhLMAY#v=onepage&q=Ansi%20sparc&f=false