We have the following indirect implication of form equivalence classes:

89 \(\Rightarrow\) 254
given by the following sequence of implications, with a reference to its direct proof:

Implication Reference
89 \(\Rightarrow\) 254 Variations of Zorn's lemma, principles of cofinality, and Hausdorff's maximal principle, Part I and II, Harper, J. 1976, Notre Dame J. Formal Logic

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

Howard-Rubin Number Statement
89:

Antichain Principle:  Every partially ordered set has a maximal antichain. Jech [1973b], p 133.

254:

\(Z(D,R,l)\): Every directed relation \((P,R)\) in which ramified subsets have least upper bounds, has a maximal element.

Comment:

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