Ramified systems
The first author's \(\alpha\)-systems from Trans. Am. Math. Soc. 298, 497- 514 (1986; Zbl 0631.03017) are extended to handle ``ramified \(\alpha\)- systems'' which entail families of sets \(\Sigma^ 0_ \beta\) uniformly in \(\beta\) with \(1\leq \beta\leq \alpha\).
scientific article; zbMATH DE number 722499