Let X be an image of
a paracomplex by a closed mapping. Then the following are proved: (1)
X is an M1-space, and this solves positively the problem proposed by J.
Nagata, (2) dimX =IndX, and (3) dimX ≦ n if and only if there exists a
σ-closure-preserving base 𝒲 for X such that dimB(W) ≦ n − 1 for every
W ∈𝒲.