Maquette by Alexander Milne Calder for the statue of William Penn atop Philadelphia City Hall.
The North American (Philadelphia newspaper)
<i>Philadelphia and Popular Philadelphians</i> (Philadelphia: The North American, 1891), p. 2.<a rel="nofollow" class="external autonumber" href="https://archive.org/stream/philadelphiapopu00phil/philadelphiapopu00phil#page/n7/mode/1up">[1]</a>