11. A non-transitory computer-readable memory device storing instructions, the instructions comprising: one or more instructions which, when executed by one or more computer devices, cause the one or more computer devices to obtain a set of one or more addresses, each address, in the set of one or more addresses, corresponding to a respective first document, the set of one or more addresses being identified or selected by a user; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to receive, from the user, a search query after obtaining the set of one or more addresses; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to obtain a set of references to second documents based on the search query, where each address, in the set of one or more addresses obtained prior to receiving the search query, is obtained independently of the set of references to the second documents and independently of the search query; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to determine whether a second document, of the second documents, is similar to the respective first document, corresponding to an address in the set of one or more addresses, based on: whether text from a body of the second document corresponds to a same topic as text associated with a body of the respective first document; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to include one of the references, corresponding to the second document, in a filtered set of references upon determining that the second document is similar to the respective first document; and one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to present the filtered set of references to the user.
11. A non-transitory computer-readable memory device storing instructions, the instructions comprising: one or more instructions which, when executed by one or more computer devices, cause the one or more computer devices to obtain a set of one or more addresses, each address, in the set of one or more addresses, corresponding to a respective first document, the set of one or more addresses being identified or selected by a user; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to receive, from the user, a search query after obtaining the set of one or more addresses; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to obtain a set of references to second documents based on the search query, where each address, in the set of one or more addresses obtained prior to receiving the search query, is obtained independently of the set of references to the second documents and independently of the search query; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to determine whether a second document, of the second documents, is similar to the respective first document, corresponding to an address in the set of one or more addresses, based on: whether text from a body of the second document corresponds to a same topic as text associated with a body of the respective first document; one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to include one of the references, corresponding to the second document, in a filtered set of references upon determining that the second document is similar to the respective first document; and one or more instructions which, when executed by the one or more computer devices, cause the one or more computer devices to present the filtered set of references to the user. 14. The non-transitory computer-readable memory device of claim 11 , where the one or more instructions to obtain the set of one or more addresses include: one or more instructions to add a first address, corresponding to a particular document that is on-topic relative to a topic of the search query, to a positive preferences list, and one or more instructions to add a second address, corresponding to another particular document that is off-topic relative to the topic of the search query, to a negative preferences list.