Article citation counts aka cited references
Many library databases provide article citation counts traditionally known as cited references. Web of Science/Biological Abstracts/Zoological Record (the Thomson Reuter databases) have until now been the standard tool in this area.
Here is more information from the Web of Science website
Many other vendors are now including cited references:
It is important to know the general criteria that are being used to create this data.
Google Scholar also tracks cited references:
Cited references can be useful in tracking research trends, finding collaborators and mentors.