Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"All sizes | Truck load of ponderosa pine, Edward Hines Lumber Co.
operations in Malheur National Forest, Grant County, Oregon (LOC) | Flickr - Photo Sharing!."
http://www.flickr.com/photos/library_of_congress/2178329189/sizes/m/in/photostream/
Flickr
CC BY.