1. US Department of Agriculture, Vegetables 2012 summary 2013 http://usda01.library.cornell.edu/usda/current/VegeSumm/VegeSumm-01-29-2013.pdf
2. US Department of Agriculture, Census of Agriculture - County Data: California 2007 http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_County_Level/California/st06_2_030_030.pdf
3. US Department of Agriculture, Census of Agriculture - County Data 2007 http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_County_Level/Washington/st53_2_030_031.pdf
4. WSU Skagit County Extension, Skagit County agriculture statistics 2012 http://skagit.wsu.edu/Agriculture/images/2011AgStats.pdf
5. Influence of high tunnel and field conditions on strawberry growth and development;Kadir;HortScience,2006