A Sketchy History Of Pencil Lead
Pencils are a fundamental product for school kids and workers around the world, so their presence is almost taken for granted. But pencils don't grown on trees folks. Here's how they came to be.
Fecha: October 12, 2016 at 07:35AM
via Digg: http://digg.com/video/pencil-history?utm_source=ifttt
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