Martel (1995) derived approximate solutions to the second order
perturbation equations in the Newtonian limit, for flat cosmological models
with a uniform component, such as nonzero cosmological constant, domain walls,
cosmic strings, massive neutrinos, or radiation background, and used these
solutions to study the growth of large-scale structures in these models. We
showed that the relationship between the present density contrast and peculiar
velocity field turns out to be a function of Omega only, independent of the
presence or nature of the uniform component.