Summon, Drew's multisciplinary 'discovery service,' includes some information about how many times a particular search result has been cited. That information comes from Web of Science and Knowledge. However, it's not the FULL information from Web of Science and Knowledge.
When you look at some particular items in Summon, you will see "Cited by \ [number\] (Web of Science)" in the lower right corner:
!summon-wos1.jpg|border=1!
Or
!summon-wos1a.jpg|border=1! Wiki Markup
Or
If you put the cursor over the "Cited By" section, a pop-up window should come up and after a slight delay, should display something like this:
Note that the more citing articles there are, the longer it will take to display.
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