1. Blumenthal, M., A. Lindstrom, C. Ooyen, and M. E. Lynch. 2012. Herb supplement sales increase 4.5 % in 2011. HerbalGram 95:60–64.
2. Brinker, F. 2005. Eclectic case histories: Psoriasis treatment with Oregon grape extracts. Journal of the American Herbalists Guild 6(1):36–39.
3. Butler, B. J. 2008. Family forest owners of the United States, 2006. General Technical Report NRS-GTR-27. Newtown Square, Pennsylvania: U.S. Department of Agriculture, Forest Service, Northern Research Station. 72 pp.
4. ———, P. D. Miles, and M. H. Hansen. 2012. National Woodland Owner Survey Tabler web-application version 1.0. Amherst, Massachusetts: U.S. Department of Agriculture, Forest Service, Northern Research Station. Available only online: http://fiatools.fs.fed.us/NWOS/tablemaker.jsp .
5. Buttolph, L., S. Vasquez, and E. T. Jones. 2011. Oregon grape root market analysis. Institute for Culture and Ecology, Portland, Oregon. 49 pp.