The Hubble Space Telescope extragalactic distance scale key project. I. The discovery of Cepheids and a new distance to M81

WL Freedman, SM Hughes, BF Madore, JR Mould, MG Lee, P Stetson, RC Kennicutt, A Turner, L Ferrarese, H Ford, JA Graham, R Hill, JG Hoessel, J Huchra, GD Illingworth