We have the following indirect implication of form equivalence classes:
| Implication | Reference |
|---|---|
| 14 \(\Rightarrow\) 49 |
A survey of recent results in set theory, Mathias, A.R.D. 1979, Period. Math. Hungar. |
| 49 \(\Rightarrow\) 30 | clear |
| 30 \(\Rightarrow\) 62 | clear |
| 62 \(\Rightarrow\) 64 |
Amorphe Potenzen kompakter Raume, Brunner, N. 1984b, Arch. Math. Logik Grundlagenforschung |
| 64 \(\Rightarrow\) 390 | clear |
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement |
|---|---|
| 14: | BPI: Every Boolean algebra has a prime ideal. |
| 49: | Order Extension Principle: Every partial ordering can be extended to a linear ordering. Tarski [1924], p 78. |
| 30: | Ordering Principle: Every set can be linearly ordered. |
| 62: | \(C(\infty,< \aleph_{0})\): Every set of non-empty finite sets has a choice function. |
| 64: | \(E(I,Ia)\) There are no amorphous sets. (Equivalently, every infinite set is the union of two disjoint infinite sets.) |
| 390: | Every infinite set can be partitioned either into two infinite sets or infinitely many sets, each of which has at least two elements. Ash [1983]. |
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