<h1>Osterbrock, Donald E.</h1>
<h2>Combined from <a href="https://data.caltech.edu">CaltechTHESIS advisor</a></h2>
<ul>
<li>Abell, George Ogden (1957) <a href="https://resolver.caltech.edu/CaltechETD:etd-05022007-092134">The Distribution of Rich Clusters of Galaxies</a>; <a href="https://doi.org/10.7907/99X5-ZM38">10.7907/99X5-ZM38</a></li>
<li>Mathis, John Samuel (1956) <a href="https://resolver.caltech.edu/CaltechETD:etd-06072004-163340">The Abundance of Helium Relative to Hydrogen in the Orion Nebula</a>; <a href="https://doi.org/10.7907/CB4D-4026">10.7907/CB4D-4026</a></li>
</ul>