Multiple representations of the same document. Turtle and Croft discuss the association of multiple representations of the same document within the same network. For example, one set of keywords might be assigned automatically, while a second set may be manually assigned. But interactions among these representations, capturing, for example, the probability that a human editor would assign the keyword INFORMATION RETRIEVAL to a document given that it is assigned the keywords INFORMATION and RETRIEVAL by an automatic indexing algorithm, must also be included.