  We consider the problem of screening of an electrically charged impurity in a
clean graphene sheet. When electron-electron interactions are neglected, the
screening charge has a sign opposite to that of the impurity, and is localized
near the impurity. Interactions between electrons smear out the induced charge
density to give a large-distance tail that follows approximately, but not
exactly, an r^{-2} behavior and with a sign which is the same as that of the
impurity.
