EXTERNPROTO HUD [ 
          field SFVec3f bboxSize 
          field SFVec3f bboxCenter 
          exposedField MFNode children 
          eventIn MFNode addChildren  
          eventIn MFNode removeChildren 
          ]  
          ["urn:inet:blaxxun.com:node:HUD",
          "http://www.blaxxun.com/vrml/protos/nodes.wrl#HUD"]