An \(\alpha_4\), not Fréchet product of \(\alpha_4\) Fréchet spaces
The authors show that there exists a functionally separable almost disjoint family on \(\omega\) and construct by means of that two \(\langle \alpha_4\rangle\)-Fréchet-Uryson-spaces the product of which is \(\langle \alpha_4\rangle\) but not Fréchet-Uryson. \(\langle\alpha_4 \rangle\)-classes were introduced by \textit{A. V. Arkhangel'skij} [Sov. Math., Dokl. 13, 1185-1189 (1972); translation from Dokl. Akad. Nauk SSSR 206, 265-268 (1972; Zbl 0275.54004); Tr. Mosk. Mat. O.-va 40, 171-206 (1979; Zbl 0447.54004)], the productivity of them was studied amongst others by \textit{T. Nogura} [Topology Appl. 21, 251-259 (1985; Zbl 0574.54005)].
functionally separable almost disjoint family
scientific article; zbMATH DE number 1538674