1. A method of information searching in a document image derived from a scanner, the method comprising: defining a key type of a referential key based on at least one type of contextual indicator of a plurality of contextual indicator types that is present in the document image; parsing successive portions of the document image to locate a first type of contextual indicator of the plurality of contextual indicator types, wherein locating the first type of contextual indicator identifies a referential key within the document image; identifying at least one portion of the document image that includes the located first type of contextual indicator; determining if the located first type of contextual indicator is determinative of the defined key type of the referential key, without knowledge of text contained within the portion of the document image that includes the located first type of contextual indicator; extracting characters from the referential key if the located first type of contextual indicator is determinative of the defined key type of the referential key; parsing the portion of the document image that includes the located first type of contextual indicator to locate a second type of contextual indicator of the plurality of contextual indicator types if the located first type of contextual indicator is not determinative of the defined key type of the referential key; determining that a combination of the located first type of contextual indicator and the located second type of contextual indicator located in the document image is determinative of the defined key type of the referential key; and extracting characters from the referential key in response to the determining that the combination of the located first type of contextual indicator and the located second type of contextual indicator located in the document image is determinative of the defined key type of the referential key.