Gradually Truncated Power law distribution - Citation of scientists Hari M. Gupta, Jose R. Campanha and Bianca A. Ferrari Unesp - Physics Dpto. - Rio Claro Sao Paulo - Brazil Abstract The number of times, a scientist is cited in other scientific publications is now an important factor in his merit consideration. Normally citation indices of highly cited scientists are available, which in turn give information only about the dynamics of the citation mechanism of this group. In the present work, we studied the statistical distribution of the citation index of Brazilian scientists working in diverse areas, through Zipf-plot technique. As it is a small sub-group within the scientific community, it can better explain the dynamics of citation index. We find that gradually truncated power law distribution can explain well citation index. The distribution of citation of most cited physicist can also be well explained. We develop a model of citation, based on positive feedback, i.e. highly cited scientist, would get better financial help, and more students, which in turn help to form a large group working in the same topic and paper is cited more times. The limiting factor comes because of limited number of articles which can be published in a particular sub-area due to limited number of scientific journal, where the article can be cited.