25. The system of claim 16 , wherein the operation of creating the plurality of anchors comprises creating multiple sets of anchors dispersed throughout the document in accordance with multiple respective anchor-placement schemes.
25. The system of claim 16 , wherein the operation of creating the plurality of anchors comprises creating multiple sets of anchors dispersed throughout the document in accordance with multiple respective anchor-placement schemes. 26. The system of claim 25 , wherein the operations further comprise using the multiple sets of anchors to generate multiple referencing addresses identifying the selected portion.