Answered By: Robert Sebek Last Updated: Sep 01, 2016 Views: 59
Google Scholar lists how many times an article has been cited based on similar citations from journals they index, which does not include citations in journals that they do not index.
Summon lists citation counts from the Web of Science database, which also does not include all journals, but is the go-to-database for these kinds of measurements. If a search results contains an article from one of the journals tracked by Web of Science, it will list the times cited count and will link to the article's record in Web of Science, which then lists each of these citing articles.
Summon will also list some Altmetrics which is tracks some of the more non-traditional counts such as downloads, mentions in social media or viewing.