Projectively Solid Sets and an N-dimensional Piccard's Theorem Lindgren, W.; Szymanski, A. — 1998 Serdica Mathematical Journal We discuss functions f : X × Y → Z such that sets of the form f (A × B) have non-empty interiors provided that A and B are non-empty sets of second category and have the Baire property.
Topological spaces which admit a compatible complete quasi-uniformity Fletcher, P.; Lindgren, W. F. — 1972 General Topology and its Relations to Modern Analysis and Algebra