Good Manufacturing Practice (GMP) is the world standard of herbal medicine and these guidelines are used, amongt testing for heavy metals, pesticides and bacteria, by Evergreen Herbs, a family-run business with 3 generations of Chinese herbal scholars bringing quality medicine to practitioners and patients alike. Keep in mind also that most herbs are coming from Taiwan, so why the quality is so high. Evergreen Herbs and Herb Safety The formulas are fantastic and bring my patients much healing! The pharmacology tomes written by John Chen and Tina Chen are a boom to phytomedicine worldwide and research is the basis of this materia medica. Order book: Chinese Medical Herbology and Pharmacology from Evergreen Herbs or Amazon.