The Hubble space telescope key project on the extragalactic distance scale. XXVIII. Combining the constraints on the Hubble constant

JR Mould, JP Huchra, WL Freedman, RC Kennicutt, L Ferrarese, HC Ford, BK Gibson, JA Graham, SMG Hughes, GD Illingworth, DD Kelson, LM Macri, BF Madore, S Sakai, KM Sebo, NA Silbermann, PB Stetson