1. Koh E, Charoenprasert S, Mitchell AE: Effect of organic and conventional cropping systems on ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 varieties of spinach (Spinacia oleracea L.). J Agric Food Chem. 2012 Mar 28;60(12):3144-50. doi: 10.1021/jf300051f. Epub 2012 Mar 20. [PubMed:22393895 ]