7Belk W P, Sunderman, F W. A survey of the accuracy of chemical analyses in clinical laboratories[-J]. American Journal of Clinical Pathology, 1947,17(11): 853-861.
8Sunderman F W. The history of proficiency testing/ quality control [J]. Clinical Chemistry, 1992, 38 (7) : 1205-1209.
9Laessig R H, Ehrmeyer S S. Proficiency testing pro- grams-promises, progress, and problems. A 40-year prospective[J]. Archives of pathology & laboratory medicine, 1988,112 (4) : 329-333.
10Sunderman F W. Forty-five years of proficiency testing [J]. Annals of Clinical and Laboratory Science, 1991, 21 (2) : 143-144.