We have the following indirect implication of form equivalence classes:

50 \(\Rightarrow\) 242
given by the following sequence of implications, with a reference to its direct proof:

Implication Reference
50 \(\Rightarrow\) 14 A survey of recent results in set theory, Mathias, A.R.D. 1979, Period. Math. Hungar.
14 \(\Rightarrow\) 233 Algebraic closures without choice, Banaschewski, B. 1992, Z. Math. Logik Grundlagen Math.
233 \(\Rightarrow\) 242 clear

Here are the links and statements of the form equivalence classes referenced above:

Howard-Rubin Number Statement
50:

Sikorski's  Extension Theorem: Every homomorphism of a subalgebra \(B\) of a Boolean algebra \(A\) into a complete Boolean algebra \(B'\) can be extended to a homomorphism of \(A\) into \(B'\). Sikorski [1964], p. 141.

14:

BPI: Every Boolean algebra has a prime ideal.

233:

Artin-Schreier theorem: If a field has an algebraic closure it is unique up to isomorphism.

242:

There is, up to an isomorphism, at most one algebraic closure of \({\Bbb Q}\).

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