20. The method according to claim 1 , further comprising: classifying each document from anion said N electronic documents as relevant or irrelevant to an issue; generating a computer display of at least one user-selected document within said N electronic documents, wherein at least some words in said user-selected, document are differentially presented depending on their contribution to said classifying of the document as relevant or irrelevant; sequentially removing certain sets of words from each individual document classified and using the text classifier to classify said document's relevance assuming said words are removed, thereby to obtain a relevance output for each set of words; and comparing said relevance output to an output obtained by using the text classifier to classify said individual document without removing any words, thereby to obtain an indication of the contribution of each set of words to the relevance of the document.
20. The method according to claim 1 , further comprising: classifying each document from anion said N electronic documents as relevant or irrelevant to an issue; generating a computer display of at least one user-selected document within said N electronic documents, wherein at least some words in said user-selected, document are differentially presented depending on their contribution to said classifying of the document as relevant or irrelevant; sequentially removing certain sets of words from each individual document classified and using the text classifier to classify said document's relevance assuming said words are removed, thereby to obtain a relevance output for each set of words; and comparing said relevance output to an output obtained by using the text classifier to classify said individual document without removing any words, thereby to obtain an indication of the contribution of each set of words to the relevance of the document. 50. The method according to claim 20 wherein said set of issues comprises a plurality of issues and said computer display includes an indication of documents relevant to a logical combination of a plurality of issues.