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.