* The Extragalactic Distance Scale by Bill Keel* The Hubble Space Telescope Key Project on the Extragalactic Distance Scale* The Hubble Constant, a historical discussion* NASA Cosmic Distance Scale* PNLF information database* The Astrophysical Journal
== External links ==* The ABC's of distances (UCLA)* The Extragalactic Distance Scale by Bill Keel* The Hubble Space Telescope Key Project on the Extragalactic Distance Scale* The Hubble Constant, a historical discussion* NASA Cosmic Distance Scale* PNLF information database* The Astrophysical Journal