Skulls of adult African elephants in Natural History Museum, from frontal. Left: African Bush Elephant shot by A.Haig in northeastern Africa. Right: African Forest Elephant shot by Stanley C. Tomkins SW of Lake Albert (Orientale Province, Democratic Republic of the Congo).
"Butterworth"
1907
<i>Proceedings of the Zoological Society of London</i> (<a rel="nofollow" class="external text" href="https://archive.org/details/proceedingsofzoo19071446zool">vol. 1907 issue 2</a>, <a rel="nofollow" class="external text" href="https://archive.org/stream/proceedingsofzoo19071446zool#page/401/mode/1up">page 401</a> and  <a rel="nofollow" class="external text" href="https://archive.org/stream/proceedingsofzoo19071446zool#page/402/mode/1up">page 402</a>)