Subbase structures in nearness spaces Wattel, E. — 1977 General topology and its relations to modern analysis and algebra IV
A general fixed point theorem Wattel, E. — 1972 General Topology and its Relations to Modern Analysis and Algebra
Compactness as an operator J. de Groot; H. Herrlich; G. E. Strecker; E. Wattel — 1969 Compositio Mathematica