https://github.com/davepinch/pinchy.cc/blob/master/content/topics/geology/usgs/publications/bulletin-1359/snippet-sec1a-greenschist.md
Geology and Mineral Resources of the Northern part of the North Cascades National Park, Washington Reconnaissance geology of the 500-square-mile wilderness north of the Skagit River, and the mineral survey that was made before it became a park. 1972