The Hirsch index is a number that synthesizes a researcher's output. It is defined as the maximum number h such that the researcher has h papers with at least h citations each. Four characterizations of the Hirsch index are suggested. The most compact one relies on the interpretation of the index as providing the number of valuable papers in an output and postulates three axioms. One, only cited papers can be valuable. Two, the index is strongly monotonic: if output x has more papers than output y and each paper in x has more citations than the most cited paper in y, then x has more valuable papers than y. And three, the minimum amount of citations under which a paper becomes valuable is different for each paper.
Egghe, L 2006 Theory and practice of the g-index. Scientometrics 69:131–152 .
Hirsch, JE 2005 An index to quantify an individual's scientific research output. Proceedings of the National Academy of Sciences of USA 102 46 16569–16572 .
Marchant, T 2009 An axiomatic characterization of the ranking based on the h-index and some other bibliometric rankings of authors. Scientometrics 80:325–342 .
Quesada, A 2009 Monotonicity and the Hirsch index. Journal of Informetrics 3:158–160 .
Quesada, A 2010 More axiomatics for the Hirsch index. Scientometrics 82:413–418 .
Woeginger, GJ 2008 An axiomatic characterization of the Hirsch-index. Mathematical Social Sciences 56:224–232 .
Woeginger, GJ 2008 A symmetry axiom for scientific impact indices. Journal of Informetrics 2:298–303 .