  I here propose an index that links the number of papers a researcher has
published with impact factors (IFs) of the journals that publish these papers.
A researcher is said to have an index z if totally z of his/her papers are
published in journals with IFs of at least z/2. The z-index, not meant to
evaluate, compare and rank scientists, is a number that hopefully conveniently
summarizes the number of publications in journals with high IFs.
