  We checked that the distribution of words in text should uniform, which gives
Heaps' law as natural result, that is, the number of types of words can be
expressed as a power law of the number of tokens within text. We developed a
``superposition'' model, which leads to an asymptotic power-law distribution of
the number of occurrences (or frequency) of words, that is, Zipf's law. The
model is well consistent with observations.
