This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Four color theorem cell tower circles. en Four color theorem While the four color problem is less interesting to cartographers it can help other areas such as cell tower placement If each cell tower broadcast channel is like color and channel colors are limited to four then the problem of where to position broadcast towers for maximum