A citation sentence is one that appears in a scientific article and cites previous work. Citation sentences have been studied and used in many applications. For example, they have been used in scientific paper summarization, automatic survey generation, paraphrase identification, and citation function classification. Citation sentences that cite multiple papers are common in scientific writing. This observation should be taken into consideration when using citation sentences in applications. For instance, when a citation sentence is used in a summary of a scientific paper, only the fragments of the sentence that are relevant to the summarized paper should be included in the summary. In this paper, we present and compare three different approaches for identifying the fragments of a citation sentence that are related to a given target reference. Our methods are: word classification, sequence labeling, and segment classification. Our experiments show that segment classification achieves the best results.