1. A method for analysing a text portion and retrieving documents relevant to the text portion, the method comprising: a) receiving an input comprising an input text portion; b) using a processor to identify at least one text term in the input text portion; c) using the processor, assigning at least one weight associated with the at least one text term; d) using the processor, to form an input local index of the at least one text term in the input text portion and at least one associated local term weight, wherein the at least one associated local term weight is determined with reference to a global term index stored in a database, the global term index comprising a plurality of global text terms and associated global text term weights, and being formed from a plurality of reference documents, wherein a representation of each of the reference documents is stored in the database; e) using the processor, querying the database to identify one or more of the reference documents of relevance with respect to the input text portion; f) outputting a representation of the identified relevant reference documents; g) displaying the relevant reference documents on a user interface, the user interface comprising input means for receiving user input with respect to each of the displayed reference documents; h) accepting user-input with respect to one or more of the displayed documents; i) using the processor, re-forming the input local term index on the basis of the user input; j) on the basis of the re-formed input local term index, using the processor to query the database to identify one or more relevant reference documents of enhanced relevance to the input text portion; and k) using the processor, outputting a representation of the further identified reference documents of enhanced relevance to the user interface for presentation to a user; wherein, the processor comprises a programmable data processing apparatus comprising instructions which execute via the processor to implement the steps (a) to (k).