# W H Lin's thesis and Hopf subalgebras of the Steenrod algebra

If $$B$$ is a subalgebra of $$A$$, you can ask whether the $$B$$-module structure on $$B$$ can be extended to give an $$A$$-module structure on $$B$$.

W H Lin, in his 1973 PhD thesis at Northwestern, showed that the only Hopf subalgebras of the mod 2 Steenrod algebra for which this can be done are the algebras $$A(n)$$ — this is the algebra generated by $$\text{Sq}^{2^i}$$ for $$i\leq n$$. Are there any electronic copies of the thesis, or at least this particular proof, available?

• this is the library entry --- no digital copy I'm afraid. Jan 10, 2020 at 21:21