Steven R. Bagley David F. Brailsford Matthew R. B. Hardy Creating reusable well-structured PDF as a sequence of component object graphic (COG) elements. 58-67 2003 conf/doceng/2003 ACM Symposium on Document Engineering http://doi.acm.org/10.1145/958220.958233 db/conf/doceng/doceng2003.html#BagleyBH03