A unification of three models for the h-index

Among existing theoretical models for the h-index, Hirschʹs original approach, the Egghe-Rousseau model, and the Glänzel-Schubert model are the three main representatives. Assuming a power-law relation or Heapsʹ law between publications and citations a unified theoretical explanation for these three models is provided. It is shown that on the level of universities, the Glänzel-Schubert model fits best.