  A scheme of evaluating an impact of a given scientific paper based on
importance of papers quoting it is investigated. Introducing a weight of a
given citation, dependent on the previous scientific achievements of the author
of the citing paper, we define the weighting factor of a given scientist.
Technically the weighting factors are defined by the components of the
normalized leading eigenvector of the matrix describing the citation graph. The
weighting factor of a given scientist, reflecting the scientific output of
other researchers quoting his work, allows us to define weighted number of
citation of a given paper, weighted impact factor of a journal and weighted
Hirsch index of an individual scientist or of an entire scientific institution.
