A certain subspace of characteristic zero of $\left(l^1\right)$

Van Dulst, D.

Compositio Mathematica, Volume 28 (1974) p. 195-201

Barreledness of subspaces of countable codimension and the closed graph theorem

Van Dulst, D.

Compositio Mathematica, Volume 24 (1972) p. 227-234

On strictly singular operators

Van Dulst, D.

Compositio Mathematica, Volume 23 (1971) p. 169-183