7. A machine readable medium storing a program which when executed by at least one processing unit analyzes a document comprising a plurality of primitive elements, the program comprising sets of instructions for: identifying a first set of hierarchically-organized lists in a first column and a second set of hierarchically-organized lists in a second column subsequent to the first column in the document, each of the first and second sets of hierarchically-organized lists comprising one or more list items identified by a list label; determining that a first list in the first set of hierarchically-organized lists continues as a second list in the second set of hierarchically-organized lists based on an analysis of the list labels of a last list item in the first list and a first list item in the second list; and storing the first list and the second list as a single list structure associated with the document.
11. The machine readable medium of claim 7 , wherein the second column is immediately after the first column in a reading order of the document.