In our pilot study we found that it's beneficial to force a cross-reference or emphasis entity as a word when the item has 2 or 3 characters.
this is 0.72% absolute improvement over supervised baseline (corresponding to 15.19% relative error reduction), and 0.33% absolute improvement over constrained decode (corresponding to 7.59% relative error reduction); the differences are both statistically significant (p < 0.001).