1. A computer implemented method for accessing to related documents by chosen keywords, the method comprising: extracting citation contexts of each document, that cites at least one document, in a database containing documents, identifying meaningful keywords/word groups from a citation context of each document, forming a citation network, an edge-labeled directed graph, where nodes are the documents; there is an edge from a citing article to a cited article and the edge is labeled by inferred keywords, constructing a table T which contains a citing document, a cited document, and the inferred keywords in a citation, receiving the keywords/word groups to initiate a search identifying citing and cited documents by searching entered keywords in the table T, forming a related document pool by adding the cited documents identified in the table T and the related document pool, ranking the documents taken to the related document pool by using any ranking algorithm.