Llibres geospacials lliures <a href="http://slashgeo.org/2011/06/07/Hundreds-Free-Geospatial-PDF-Books-National-Academies-Press">http://slashgeo.org/2011/06/07/Hundreds-Free-Geospatial-PDF-Books-National-Academies-Press</a><br>
<br>Raf<br>