We have the following indirect implication of form equivalence classes:

172 \(\Rightarrow\) 19
given by the following sequence of implications, with a reference to its direct proof:

Implication Reference
172 \(\Rightarrow\) 34 On hereditarily countable sets, Jech, T. 1982, J. Symbolic Logic
34 \(\Rightarrow\) 19 Sur les fonctions representables analytiquement, Lebesgue, H. 1905, J. Math. Pures Appl.

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

Howard-Rubin Number Statement
172:

For every infinite set \(S\), if \(S\) is hereditarily countable  (that is, every \(y\in TC(S)\) is countable) then \(|TC(S)|= \aleph_{0}\).

34:

\(\aleph_{1}\) is regular.

19:

A real function is analytically representable if and only if it is in Baire's classification. G.Moore [1982], equation (2.3.1).

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