When we learn from books or daily experience, we make associations and draw inferences on the basis of information that is insufficient for under- standing. One example of insufficient information may be a small sample derived from observing experiments. With this perspective, the need for de- veloping a better understanding of the behavior of a small sample presents a problem that is far beyond purely academic importance. During the past 15 years considerable progress has been achieved in the study of this issue in China. One distinguished result is the principle of in- formation diffusion....