L'USGS digitalitzarā el seu fons de topogrāfics, unes 200mil peces <a href="http://blogs.smithsonianmag.com/travel/2012/07/a-treasure-trove-of-old-maps-at-your-fingertips/">http://blogs.smithsonianmag.com/travel/2012/07/a-treasure-trove-of-old-maps-at-your-fingertips/</a><br>
<br>Raf<br>