AutoCAD 2012 DXF Reference February 2011 © 2011 Autodesk, Inc. All Rights Reserved. Except as otherwise permitted by Autodesk, Inc., this publication, or parts thereof, may not be reproduced in any......(optional; always appears in pairs with the 13, 23, 33 codes):71...point23, 33 Each 71/13,23,33 pair defines the UCS origin for a...