Inhomogeneities and the Intergalactic Distance-Redshift Relation
  Modifications in Friedmann-Lemaitre-Robertson-Walker (FLRW) Hubble diagrams caused by mass density inhomogeneities are used to illustrate possible effects on a determination of the mass parameter $\Omega_m$ and the cosmological constant $\Lambda$. The values of these parameters inferred from a given set of observations depend on the fractional amount of matter in inhomogeneities and can differ from those obtained by using standard FLRW Hubble diagrams by as much as a factor of two. 
R. Kantowski