Some properties of $\beta$-$\eta$-normal forms in $\lambda$-K-calculus (Alcune proprietá delle forme $\beta$-$\eta$-normali nel $\lambda$-K-calcolo)

This is a plain English translation of [Böh68], originally in Italian, by Chun Tian. All footnotes (and citations only found in footnotes, of course) are added by the translator.