These methods measure the mass associated with galaxies and clusters on scales of order one to a few h-1Mpc. The structure is assumed to have grown from small initial fluctuations via GI, and the methods involve nonlinear dynamics of virialized systems. The cosmological constant is irrelevant; the structure at low redshift is insensitive to .
Several additional physical quantities are now involved, such as the baryonic contribution to the universal mass density, b. The complex relation between galaxies and mass, termed ``biasing'', enters as a crucial unknown on these galactic scales, and issues of gas dynamics are important. These complications introduce severe uncertainties into the estimates of m.