We have the following indirect implication of form equivalence classes:
| Implication | Reference |
|---|---|
| 3 \(\Rightarrow\) 9 |
Cardinal addition and the axiom of choice, Howard, P. 1974, Bull. Amer. Math. Soc. |
| 9 \(\Rightarrow\) 84 |
Definitions of finite, Howard, P. 1989, Fund. Math. |
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement |
|---|---|
| 3: | \(2m = m\): For all infinite cardinals \(m\), \(2m = m\). |
| 9: | Finite \(\Leftrightarrow\) Dedekind finite: \(W_{\aleph_{0}}\) Jech [1973b]: \(E(I,IV)\) Howard/Yorke [1989]): Every Dedekind finite set is finite. |
| 84: | \(E(II,III)\) (Howard/Yorke [1989]): \((\forall x)(x\) is \(T\)-finite if and only if \(\cal P(x)\) is Dedekind finite). |
Comment: