https://www.chicoer.com/2018/05/29/butte-walnut-acreage-tops-california-counties-almond-acreage-down-to-ninth/
http://www.westernfarmpress.com/orchard-crops/walnut-acreage-increased-10-percent-2015
http://www.dailydemocrat.com/business/20180505/mariani-nut-company-continues-to-grow
http://www.westernfarmpress.com/tree-nuts/walnut-product-innovations-creating-more-demand