Research Article
Larger Thyroid Volume and Adequate Iodine Nutrition in Chinese Schoolchildren: Local Normative Reference Values Compared with WHO/IGN
Figure 1
Sampling counties in Zhejiang Province, China. Thirty counties (gray areas) from Zhejiang Province, in the east coastal region of China, which covers 89 counties, were selected by using a probability-proportionate-to-size sampling method.