1. Mappings and spaces;Arhangel'skii;Russian Math. Surveys,1966
2. Extensions of topological spaces;Banaschewski;Canad. Math. Bull.,1965
3. M.G. Bell, First countable pseudocompactifications, to appear.
4. β(X) can be Fréchet;Berner;Proc. Amer. Math. Soc.,1980
5. First-countable and countable spaces all compactifications of which contain βN;van Douwen;Fund. Math.,1979