Justus Bier (1899–1990)
Unknown author<span style="display: none;">Unknown author</span>
John Simon Guggenheim Memorial Foundation; <a rel="nofollow" class="external free" href="https://www.gf.org/wp-content/uploads/2014/07/Justus-Bier-Fine-Arts-Research-1953-1956.jpg">https://www.gf.org/wp-content/uploads/2014/07/Justus-Bier-Fine-Arts-Research-1953-1956.jpg</a>