title = {A formal derivation of Heaps' Law},
author = {D. C. van Leijenhorst and Th. P. van der Weide}, journal = {Information Sciences}, number = {2-4}, pages = {263-272}, url = {citeseer.ist.psu.edu/grootjen03formal.html}, volume = {170}, year = {2005},
keywords = {models nlp zipf }
::