  In this paper, we consider a class of important nonlinear elliptic equations
$$\Delta u + a(x)u\log u + b(x)u = 0$$ on a collapsed complete Riemannian
manifold and its parabolic counterpart under integral curvature conditions,
where $a(x)$ and $b(x)$ are two $C^1$-smooth real functions. Some new local
gradient estimates for positive solutions to these equations are derived by
Moser's iteration provided that the integral Ricci curvature is small enough.
Especially, some classical results are extended by our estimates and a few
interesting corollaries are given. Furthermore, some global gradient estimates
are also established under certain geometric conditions. Some estimates
obtained in this paper play an important role in a recent paper by Y. Ma and B.
Wang [17], which extended and improved the main results due to B. Wang [29] to
the case of integral Ricci curvature bounds.
