Oulu Airport in the 1950s.
Unknown author<span style="display: none;">Unknown author</span>
<cite class="book" style="font-style:normal" id="Reference-Huttunen-1959">Huttunen, Pentti; et al. (1959)      <i> Oulu ympäristöineen teknillisen nousun vaiheissa</i>, <a href="https://en.wikipedia.org/wiki/en:Oulu" class="extiw" title="w:en:Oulu"><span title="city in the region of Northern Ostrobothnia in Finland">Oulu</span></a>:  Oulun Teknillinen Seura ry, p. 73  <small></small></cite>