 The definitions are easily seen to imply that all these combinators depend on both \(\textsf{S}\) and \(\textsf{K}\), but it is not obvious from the definitions that the defined combinators are mutually independent, that is, that none of the listed combinators is definable from another one. (Clearly, some subsets suffice to define some of the combinators.) We do not intend to give an exhaustive list of interdefinability between various subsets of these combinators, but to hint at the multiplicity and intricacy of such definitions, we list a handful of them. We also introduce two further combinators \(\textsf{S}^\prime\) and \(\textsf{R}\).