Anaphora are hidden descriptions found in discourse, which refer to explicitly mentioned entities of the discourse e.g. Mary loves tennis, she plays everyday. Humans can expand anaphors into fuller descriptions with ease by using intuitive world knowledge, which links the anaphor with a suitable entity of the discourse. In the example above it is obvious to us that she may be expanded into, or refer to, the previously mentioned female entity Mary. As humans we do not allow she to refer to tennis, as intuitively we know that the female she must refer to another female entity. Modelling anaphora resolution or expansion is a difficult task as so much of what is communicated is implicit in discourse. This thesis investigates the historical development of existing methods of resolving anaphors within discourse, and aims at implementing one such mechanism using a small fragment of English.