6. A non-transitory computer-readable medium storing instructions, the instructions comprising: one or more instructions that, when executed by at least one processor, cause the at least one processor to: receive a first document; identify links in a plurality of second documents that each include a link to the first document; determine a second document of the plurality of second documents that has been used to access the first document more frequently than any other second document of the plurality of second documents; extract concepts associated with the determined second document; and associate the extracted concepts with the first document, at least one extracted concept, of the extracted concepts, being associated with anchor text in the determined second document.
9. The non-transitory computer-readable medium of claim 6 , the instructions further comprising: one or more instructions that, when executed by at least one processor, cause the at least one processor to: identify links in the first document pointing from the first document to a plurality of third documents; determine a third document of the plurality of third documents that has been used to access the first document more frequently than any other third document of the plurality of third documents; extract other concepts associated with the determined third document; and associate the other concepts with the first document.