We have the following indirect implication of form equivalence classes:
			
| Implication | Reference | 
|---|---|
| 407 \(\Rightarrow\) 14 | Effective equivalents of the Rasiowa-Sikorski lemma, Bacsich,  P. D. 1972b, J. London Math. Soc. Ser. 2. | 
| 14 \(\Rightarrow\) 270 | Restricted versions of the compactness theorem, Kolany,  A. 1991, Rep. Math. Logic | 
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement | 
|---|---|
| 407: | Let \(B\) be a Boolean algebra, \(b\) a non-zero element of \(B\) and \(\{A_i: i\in\omega\}\) a sequence of subsets of \(B\) such that for each \(i\in\omega\), \(A_i\) has a supremum \(a_i\). Then there exists an ultrafilter \(D\) in \(B\) such that \(b\in D\) and, for each \(i\in\omega\), if \(a_i\in D\), then \(D\cap\ A_i\neq\emptyset\). | 
| 14: | BPI: Every Boolean algebra has a prime ideal. | 
| 270: | \(CT_{\hbox{fin}}\): The compactness theorem for propositional logic restricted to sets of formulas in which each variable occurs only in a finite number of formulas. | 
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