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Historical trend map of Ascaris egg-positive percentage among elementary school children. Ascaris egg-positive percentages in 1960, 1966 and 1973 are represented in gray scale. These maps were created using statistical data from the Ministry of Education, Culture, Sports, Science and Technology, Japan [18–20] and the website Hakuchizu nurinuri (https://n.freemap.jp), which provides copyright-free maps. The maps were then edited with Adobe Photoshop version CS 5.1
