<a href="https://en.wikipedia.org/wiki/Booster_engine" class="extiw" title="w:Booster engine">Booster engine</a> installation layout.
<a href="https://en.wikipedia.org/wiki/1922_Locomotive_Cyclopedia_of_American_Practice" class="extiw" title="en:1922 Locomotive Cyclopedia of American Practice">1922 Locomotive Cyclopedia of American Practice</a>