·Problem:
 LM probabilities cannot be determined upon transition to lextree root nodes
 ·Root
 nodes shared among several unrelated words
 ·Several
 solutions possible:
 ·Incremental
 evaluation, using composite LM scores
 ·Lextree
 replication (Ney, Antoniol)
 ·Rescoring
 at every node (BBN)
 ·Post-tree
 evaluation (Sphinx-II)