Jean-Yves Vion-Dury Emmanuel Pietriga A Formal Study of a Visual Language for the Visualization of Document Type Definition. 52-59 2001 conf/vl/2001 HCC http://csdl.computer.org/comp/proceedings/hcc/2001/0474/00/04740052abs.htm db/conf/vl/hcc2001.html#Vion-DuryP01