protected sealed override void completeNewGTTSources(RGTTSD gttd)
 {
 }
 protected sealed override void propagateDownGTTISources(RGTTSD gttd)
 {
 }
 protected sealed override void mergeSources(RGTTSD gttdFrom, RGTTSD gttdTo)
 {
 }
 protected override sealed void propagateGTTINLGTTs(RGTTSD gttd)
 {
     gttd.clearNLTs();
 }