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.